Routing Configuration Guide for Cisco NCS 540 Series Routers, IOS XR Release 24.1.x, 24.2.x, 24.3.x

BFD Overview

Bidirectional forwarding detection (BFD) provides low-overhead, short-duration detection of failures in the path between adjacent routers. BFD allows a single mechanism to be used for failure detection over any media and at any protocol layer, with a wide range of detection times and overhead. The fast detection of failures provides immediate reaction to failure in the event of a failed link or neighbor.

Restrictions

These restrictions apply to BFD:

Demand mode is not supported in Cisco IOS XR software.
BFD echo mode and encryption are not supported.
BFD hardware offload for IPv4 is supported.
Only the static, OSPF, BGP and IS-IS applications are supported on BFD.
BFD dampening for IPv4 is supported starting from Cisco IOS XR Release 6.3.2.
BFD supports BFDv6 on bundle-ether for VRF BGP IPv6 single-hop.
BFD multihop over non-IP core (Label Distribution Protocol or Segment Routing) is supported starting from IOS XR Release 7.1.1.

BFD is only supported in IP core. It cannot coexist with Label distribution Protocol, or Segment Routing, or Traffic Engineering in the core. This is applicable for releases prior to IOS XR Release 7.1.1.
BFD over bundle feature is supported only in IETF mode.
Dampening extensions for BFD are not supported.
Starting from Cisco IOS XR Release 6.6.1, BFD over VRF is supported.
Starting from Cisco IOS XR Release 7.2.1, BFD support over VRRP interface is supported.
Egress IPv4 ACLs block all traffic, including router-generated traffic for the following routers and line cards:
- NC57-24DD
- NC57-18DD-SE
- NC57-36H-SE
- NC57-36H6D-S
- NC57-MOD-S
- NCS-57B1-6D24-SYS
- NCS-57B1-5DSE-SYS
For all other routers and line cards, egress IPv4 ACLs do not block certain router-generated traffic, such as ICMP messages.

BFD Timers

The BFD timers are applicable on the following NCS 540 variants:

Medium Density XR NCS 540 - N540-24Z8Q2C-SYS, N540-28Z4C-SYS, N540X-ACC-SYS, N540-ACC-SYS

Medium Density XR NCS 540 - N540-28Z4C-SYS-A, N540-28Z4C-SYS-D, N540X-16Z4G8Q2C-A, N540X-16Z4G8Q2C-D, N540X-16Z8Q2C-D, N540-12Z20G-SYS-A,N540-12Z20G-SYS-D, N540X-12Z16G-SYS-A, N540X-12Z16G-SYS-D

Small Density XR NCS 540 - N540X-6Z18G-SYS-A, N540X-6Z18G-SYS-D, N540X-8Z16G-SYS-A, N540X-8Z16G-SYS-D

Note

The router uses six unique timer profiles. Four timers profiles are available when you configure BFD over Bundle (BoB). Up to five timers profiles are available when you configure BoB.

Table 1. IPv4 BFD Timers
Type of BFD Session	Minimum Timer Supported	Default/Minimum-interval timer (Multipliers)	Supported Timer Profiles (Up to 6 unique timers profiles)
Single Hop	4ms	3	Any
BFD over Bundle Members (BoB)	4ms	3	Any
BFD over Logical bundle (BLB)	50ms	3	Any
BGP Multi Hop	50ms	3	Any

Table 2. IPv6 BFD Timers
Type of BFD Session	Minimum Timer Supported	Default/Minimum- interval timer (Multipliers)	Supported Timer Profile (Up to 6 unique timer profiles)	Maximum Scale depending on Minimum Interval
Single Hop	4ms	3	Any	150 (with 8ms and above, all 256 sessions are configurable)
BFD over Bundle Members (BoB)	4ms	3	Any	150ms (with 8ms and above, all 256 sessions are configurable)
BFD over Logical bundle (BLB)	50ms	3	Any	256
BGP Multi Hop	50ms	3	Any	256

Enable and Disable IPv6 Checksum Calculations for BFD on a Router

Perform the following steps to configure IPv6 checksum calculations for BFD on a Router.


RP/0/RP0/CPU0:router(config)# bfd
RP/0/RP0/CPU0:router(config-bfd-if)# ipv6 checksum disable
RP/0/RP0/CPU0:router(config-bfd-if)# commit

Configure BFD Under a Dynamic Routing Protocol or Use a Static Route

To establish a BFD neighbor, complete at least one of the following procedures to configure BFD under a dynamic routing protocol or to use a static route:

Enable BFD for OSPF on an Interface

Perform the following steps to configure BFD for Open Shortest Path First (OSPF) on an interface. The steps in the procedure are common to the steps for configuring BFD on IS-IS; only the command mode differs.

Note

BFD per interface configuration is supported for OSPF and IS-IS only.


Router# configure

/* Enter OSPF configuration mode to configure the OSPF routing process. */
Router(config)# router ospf 0

/* Set the BFD minimum interval. The range is from 15 to 30000 milliseconds. */
Router(config-ospf)# bfd minimum-interval 6500

/* Set the BFD multiplier. */
Router(config-ospf)# bfd multiplier 7

/* Configure an Open Shortest Path First (OSPF) area. */
Router(config-ospf)# area 0

/* Enter interface configuration mode. */
Router(config-ospf-ar)# interface gigabitEthernet 0/3/0/1

/* Enable BFD to detect failures in the path between adjacent forwarding engines. */
Router(config-ospf-ar-if)# bfd fast-detect

Running Configuration


configure 
  router ospf 0
  bfd minimum-interval 6500
  bfd multiplier 7
   area 0
    interface gigabitEthernet 0/3/0/1
     bfd fast-detect

Verification

Verify that BFD is enabled on the appropriate interface.

Router(config-ospf-ar-if)# show run router ospf

 router ospf 0
 bfd minimum-interval 6500
 bfd multiplier 7
 area 0
 interface gigabitEthernet 0/3/0/1
 bfd fast-detect

/* Verify the details of the IPv4 BFD session in the source router. */

Router# show bfd session

Interface  Dest Addr  Local det time(int*mult)  State  Echo  Async   H/W   NPU
---------  ---------  --------  -------------   -----  ----  -----   ---   ---
Te0/0/0/0  10.23.1.2  0s(0s*0)  300ms(100ms*3)  UP     Yes                0/RP0/CPU0
BE3739     10.23.1.2  n/a       n/a             UP     No    n/a

Enable BFD over BGP

Perform the following steps to configure BFD over BGP. The following example shows how to configure BFD between autonomous system 65000 and neighbor 192.168.70.2:

Router# configure
Router(config)# router bgp 65000
Router(config-bgp)# bfd multiplier 2
Router(config-bgp)# bfd minimum-interval 20
Router(config-bgp)# neighbor 192.168.70.24
Router(config-bgp-nbr)# remote-as 2
Router(config-bgp-nbr)# bfd fast-detect
Router(config-bgp-nbr)# commit
Router(config-bgp-nbr)# end

Running Configuration


 router bgp 65000
  bfd multiplier 2
  bfd minimum-interval 20
  neighbor 192.168.70.24
  remote-as 2
  bfd fast-detect
  commit
  end

Verification

Verify that BFD has been enabled over BGP.

Router# show run router bgp
router bgp 65000
  bfd multiplier 2
  bfd minimum-interval 20
  neighbor 192.168.70.24
  remote-as 2
  bfd fast-detect

Enable BFD on an IPv4 Static Route

The following procedure shows how to enable BFD on an IPv4 static route.


RP/0/RSP0/CPU0:router# configure

/*Enter static route configuration mode to configure static routing. */
RP/0/RSP0/CPU0:router(config)# router static

/* Enable BFD fast-detection on the specified IPV4 unicast destination address prefix and on the forwarding next-hop address.*/
RP/0/RSP0/CPU0:router(config-static)# address-family ipv4 unicast 10.2.2.0/24 10.6.0.1 bfd fast-detect minimum-interval 1000 multiplier 5

RP/0/RSP0/CPU0:router(config-static)# commit

Running Configuration


configure 
 router static
  address-family ipv4 unicast 10.2.2.0/24 10.6.0.1 bfd fast-detect minimum-interval 1000 multiplier 5
  commit

Verification

Verify that BFD is enabled on the appropriate interface.

RP/0/RSP0/CPU0:router# show run router static address-family ipv4 unicast

router static
 address-family ipv4 unicast
  10.2.2.0/24 10.6.0.1 bfd fast-detect minimum-interval 1000 multiplier 5
   commit
 !
!

Enable BFD on an IPv6 Static Route

The following procedure describes how to enable BFD on a IPv6 static route.


RP/0/RP0/CPU0:router# configure

/* Enter static route configuration mode to configure static routing.  */
RP/0/RP0/CPU0:router(config)# router static

/* Enable BFD fast-detection on the specified IPv6 unicast destination address prefix and on the forwarding next-hop address. */
/* BFD sessions are established with the next hop 2001:0DB8:D987:398:AE3:B39:333:783 when it becomes reachable. */

RP/0/RP0/CPU0:router(config-static)# address-family ipv6 unicast  2001:0DB8:C18:2:1::F/64 2001:0DB8:D987:398:AE3:B39:333:783 bfd fast-detect minimum-interval 150 multiplier 4

RP/0/RP0/CPU0:router(config-static-vrf)# commit

Running Configuration


configure 
 router static
  address-family ipv6 unicast 2001:0DB8:C18:2:1::F/64 2001:0DB8:D987:398:AE3:B39:333:783 bfd fast-detect minimum-interval 150 multiplier 4
  commit

Verification

Verify that BFD is enabled on the appropriate interface.

RP/0/RP0/CPU0:router# show run router static address-family ipv6 unicast

 configure 
 router static
 address-family ipv6 unicast 2001:0DB8:C18:2:1::F/64 2001:0DB8:D987:398:AE3:B39:333:783 bfd fast-detect minimum-interval 150 multiplier 4
  commit

Clear and Display BFD Counters

The following procedure describes how to display and clear BFD packet counters. You can clear packet counters for BFD sessions that are hosted on a specific node or on a specific interface.


RP/0/RP0/CPU0:router# show bfd counters all packet location 0/3/cpu0
RP/0/RP0/CPU0:router# clear bfd counters all packet location 0/3/cpu0
RP/0/RP0/CPU0:router# show bfd counters all packet location 0/3/cpu0

BFD over Bundle

BFD Over Bundle (BoB) (RFC 7130) has a BFD session on each bundle member. BOB verifies the ability for each member link to be able to forward Layer 3 packets.

For BFD over Bundle, the BFD client is bundlemgr. When BFD detects a failure on a bundle member, bundlemgr removes that member from the bundle. If there are not enough members to keep the bundle up, then the main Bundle-Ether interface will go down so that all routing protocols running on the main bundle interface or a subinterface will detect an interface down.

BoB does not provide a true Layer 3 check and is not supported on subinterfaces. However, subinterfaces will go down at the same time as the main interface.

Configure BFD Over Bundle

Perform the following tasks to configure the BOB feature:

Enable BFD sessions on bundle members
Specify the BFD destination address on a bundle
Configure the minimum thresholds for maintaining an active bundle
Configure BFD packet transmission intervals and failure detection times on a bundle

Configure BFD over bundles IETF mode support on a per-bundle basis


/* Enable BFD sessions on bundle members */
Router(config)# interface Bundle-Ether 1
Router(config-if)# bfd address-family ipv4 fast-detect
Router(config-if)# bfd mode ietf

/* Specify the BFD destination address on a bundle */
Router(config)# interface Bundle-Ether 1
Router(config-if)# bfd address-family ipv4 destination 10.20.20.1
	 
/* Configure the minimum thresholds for maintaining an active bundle */
Router(config)# interface Bundle-Ether 1
Router(config-if)# bundle minimum-active bandwidth 580000
Router(config-if)# bundle minimum-active links 2

/* Configure BFD packet transmission intervals and failure detection times on a bundle */
Router(config)# interface Bundle-Ether 1
Router(config-if)# bfd address-family ipv4 minimum-interval 2000
Router(config-if)# bfd address-family ipv4 multiplier 30

/* Configure BFD over bundles IETF mode support on a per-bundle basis */
Router(config)# interface Bundle-Ether 1
Router(config-if)# bfd mode ietf
Router(config-if)# bfd address-family ipv4 fast-detect

BFD over Bundle

BFD over Bundle feature enables BFD sessions to monitor the status of individual bundle member links. BFD notifies the bundle manager immediately when one of the member links goes down, and reduces the bandwidth used by the bundle.

Restrictions for BFD over Bundle

The following are the restrictions in using BFD over Bundle feature:

It is only supported in IETF mode.
It is only supported on the main bundle interface; it is not supported on bundle subinterfaces.
It is not supported on routing protocols, such as OSPF, ISIS, and BGP.
When the BFD timer is configured to 3.3 ms, which is the most aggressive timer, 256 sessions can be brought up.
If BFD timer is configured to greater than 100 ms, 300 BFD sessions can be brought up simultaneously.
BFD echo mode and encryption is not supported.
BFD dampening is not supported.

Configure BFD over Bundle

Configuring BFD over bundle involves the following steps:

Specify the mode, BFD packet transmission intervals, and failure detection times on a bundle.

Note

Repeat the same configuration steps in the destination router.


/* Enable and Disable IPv6 checksum calculations for BFD on a router. */

Router(config-if)# bfd
Router(config-bfd-if)# ipv6 checksum disable 
Router(config-bfd-if)# dampening disable
Router(config-bfd-if)# commit

/* Specify the mode, BFD packet transmission intervals, and failure detection times on a bundle */

Router(config)# interface Bundle-Ether 3739
Router(config-if)# bfd mode ietf
Router(config-if)# bfd address-family ipv4 multiplier 3
Router(config-if)# bfd address-family ipv4 destination 10.23.1.2
Router(config-if)# bfd address-family ipv4 fast-detect
Router(config-if)# bfd address-family ipv4 minimum-interval 100
Router(config-if)# bfd address-family ipv6 multiplier 3
Router(config-if)# bfd address-family ipv6 destination 2001:DB8:1::2
Router(config-if)# bfd address-family ipv6 fast-detect
Router(config-if)# bfd address-family ipv6 minimum-interval 100
Router(config-if)# ipv4 address 10.23.1.1 255.255.255.252
Router(config-if)# ipv6 address 2001:DB8:1::2/120
Router(config-if)# load-interval 30
Router(config-if)# commit
Router(config)# interface TenGigE 0/0/0/0
Router(config-if)# bundle id 3739 mode active

Running Configuration


bfd
 ipv6 checksum disable 
 dampening disable!
 !

interface Bundle-Ether3739
 bfd mode ietf
 bfd address-family ipv4 multiplier 3
 bfd address-family ipv4 destination 10.23.1.2
 bfd address-family ipv4 fast-detect
 bfd address-family ipv4 minimum-interval 100
 bfd address-family ipv6 multiplier 3
 bfd address-family ipv6 destination 2001:DB8:1::2
 bfd address-family ipv6 fast-detect
 bfd address-family ipv6 minimum-interval 100
 ipv4 address 10.23.1.1 255.255.255.252
 ipv6 address 2001:DB8:1::2/120
 load-interval 30
 !

interface TenGigE 0/0/0/0
 bundle id 3739 mode active

Verification

The following show command outputs displays the status of BFD sessions on bundle members:


/* Verify the details of the IPv4 BFD session in the source router. */

Router# show bfd session

Interface  Dest Addr  Local det time(int*mult)  State  Echo  Async   H/W   NPU
---------  ---------  --------  -------------   -----  ----  -----   ---   ---
Te0/0/0/0  10.23.1.2  0s(0s*0)  300ms(100ms*3)  UP     Yes                0/RP0/CPU0
BE3739     10.23.1.2  n/a       n/a             UP     No    n/a


/* Verify the details of the IPv4 BFD session in the destination router. */

Router# show bfd session

Interface   Dest Addr  Local det  time(int*mult) State   Echo   Async   H/W   NPU
----------  ---------- --------   -------------- -----  ----   -----   ---   ---
Te0/6/0/0   10.23.1.1  0s(0s*0)   300ms(100ms*3) UP      No     n/a
BE3739      10.23.1.1  n/a        n/a            UP      No     n/a


/* Verify the details of the IPv6 BFD session in the source router. */

Router# show bfd ipv6 session
Interface  Dest Addr  Local det  time(int*mult) State      H/W     NPU       Echo Async
---------- ---------- ---------- -------------- ------     ------  ------    ---- ----
Te0/0/0/0  10:23:1::2 Yes                       0/RP0/0s (0s*0) 00ms(100ms*3) UP

BE3739     10:23:1::2 No                        n/a        n/a      n/a       UP

/* Verify the details of the IPv6 BFD session in the destination router. */

Router# show bfd ipv6 session
Interface  Dest Addr  Local det time(int*mult) State    H/W NPU           Echo  Async 
---------- ---------- --------- -------------- -------  --- ---           ----  ----
Te0/6/0/0  10:23:1::1 No        n/a            0s(0s*0)     300ms(100ms*3)  UP
BE3739     10:23:1::1 No        n/a            n/a          n/a             UP

Configuration Example

Enter the OSPF configuration mode to configure the OSPF routing process.

Router(config)# router ospf 0
Router(config)# configure LDP-IGP synchronization
Router(config)# mpls ldp sync
Router(config)# enable LDP auto-configuration for a specified OSPF instance
Router(config)# mpls ldp auto-config

Configure a BFD over Bundle Session on an Unnumbered Interface.

Router(config)# interface Bundle-Ether1

Set the BFD minimum interval.

Router(config)# bfd minimum-interval 999

Enables BFD between the local networking devices and the neighbor whose IP address you configured to be a BGP peer.

Router(config)# bfd fast-detect

Set the BFD multiplier.

Router(config)# bfd multiplier 3

Running Configuration

!
router ospf 1
log adjacency changes
router-id 10.0.0.4
mpls ldp sync
mpls ldp auto-config
prefix-suppression
auto-cost reference-bandwidth 1000000
area 0
  interface Bundle-Ether1
   bfd minimum-interval 999
   bfd fast-detect
   bfd multiplier 3
   network point-to-point
  !
!
bfd
multipath include location 0/RP0/CPU0
!

Enabling BFD on a BGP Neighbor

BFD can be enabled per neighbor, or per interface. This task describes how to enable BFD for BGP on a neighbor router.

Procedure

	Command or Action	Purpose
Step 1	configure Example: `RP/0/RP0/CPU0:router# configure`	Enters mode.
Step 2	router bgp `autonomous-system-number` Example: `RP/0/RP0/CPU0:router(config)# router bgp 120`	Enters BGP configuration mode, allowing you to configure the BGP routing process.
Step 3	neighbor `ip-address` Example: `RP/0/RP0/CPU0:router(config-bgp)# neighbor 172.168.40.24`	Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer. This example configures the IP address 172.168.40.24 as a BGP peer.
Step 4	remote-as `autonomous-system-number` Example: `RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 2002`	Creates a neighbor and assigns it a remote autonomous system. This example configures the remote autonomous system to be 2002.
Step 5	bfd fast-detect Example: `RP/0/RP0/CPU0:router(config-bgp-nbr)# bfd fast-detect`	Enables BFD between the local networking devices and the neighbor whose IP address you configured to be a BGP peer in Step 3. In the example in Step 3, the IP address 172.168.40.24 was set up as the BGP peer. In this example, BFD is enabled between the local networking devices and the neighbor 172.168.40.24.
Step 6	bfd minimum-interval `milliseconds` Example: `RP/0/RP0/CPU0:router(config-bgp-nbr)#bfd minimum-interval 6500`	Sets the BFD minimum interval. Range is 4-30000 milliseconds.
Step 7	bfd multiplier `multiplier` Example: `RP/0/RP0/CPU0:router(config-bgp-nbr)#bfd multiplier 7`	Sets the BFD multiplier. This is optional, the minimum is 3 and by default the multiplier will be 3 for all protocols
Step 8	Use the commit or end command.	commit —Saves the configuration changes and remains within the configuration session. end —Prompts user to take one of these actions: Yes — Saves configuration changes and exits the configuration session. No —Exits the configuration session without committing the configuration changes. Cancel —Remains in the configuration session, without committing the configuration changes.

Enabling BFD for OSPF on an Interface

The following procedures describe how to configure BFD for Open Shortest Path First (OSPF) on an interface. The steps in the procedure are common to the steps for configuring BFD on IS-IS ; only the command mode differs.

Procedure

Command or Action Purpose

Step 1

configure

Example:


RP/0/RP0/CPU0:router# configure

Enters mode.

Step 2

router ospf process-name

Example:


RP/0/RP0/CPU0:router(config)# router ospf 0

Enters OSPF configuration mode, allowing you to configure the OSPF routing process.

Note

To configure BFD for IS-IS, enter the corresponding configuration mode.

Step 3

area area-id

Example:


RP/0/RP0/CPU0:router(config-ospf)# area 0

Configures an Open Shortest Path First (OSPF) area.

Replace area-id with the OSPF area identifier.

Step 4

interface type interface-path-id

Example:


RP/0/RP0/CPU0:router(config-ospf-ar)# interface TengigabitEthernet 0/3/0/1

Enters interface configuration mode and specifies the interface name.

Step 5

bfd fast-detect

Example:


RP/0/RP0/CPU0:router(config-ospf-ar-if)# bfd fast-detect

Enables BFD to detect failures in the path between adjacent routers.

Step 6

bfd minimum-interval milliseconds

Example:


RP/0/RP0/CPU0:router(config-ospf-ar-if)# bfd minimum-interval 6500

Sets the BFD minimum interval. Range is 4-30000 milliseconds.

This example sets the BFD minimum interval to 6500 milliseconds.

Step 7

bfd multiplier multiplier

Example:


RP/0/RP0/CPU0:router(config-ospf-ar-if)# bfd multiplier 7

Sets the BFD multiplier. This is optional, the minimum is 3 and by default the multiplier will be 3 for all protocols.

This example sets the BFD multiplier to 7.

Step 8

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

Yes — Saves configuration changes and exits the configuration session.
No —Exits the configuration session without committing the configuration changes.
Cancel —Remains in the configuration session, without committing the configuration changes.

Enabling BFD on a Static Route

The following procedure describes how to enable BFD on a static route.

Procedure

	Command or Action	Purpose
Step 1	configure Example: `RP/0/RP0/CPU0:router# configure`	Enters mode.
Step 2	router static Example: `RP/0/RP0/CPU0:router(config)# router static`	Enters static route configuration mode, allowing you to configure static routing.
Step 3	address-family ipv4 unicast `address` `nexthop` Example: `RP/0/RP0/CPU0:router(config-static)# address-family ipv4 unicast 10.2.2.0/24 10.6.0.2`	Enables BFD fast-detection on the specified IPv4 unicast destination address prefix and on the forwarding next-hop address.
Step 4	interface `type interface-path-id` Example: `RP/0/RP0/CPU0:router(config-static)# interface TengigabitEthernet 0/3/0/1`	Enters interface configuration mode and specifies the interface name.
Step 5	bfd fast-detect Example: `RP/0/RP0/CPU0:router(config-static-if)# bfd fast-detect`	Enables BFD to detect failures in the path between adjacent forwarding engines.
Step 6	Use the commit or end command.	commit —Saves the configuration changes and remains within the configuration session. end —Prompts user to take one of these actions: Yes — Saves configuration changes and exits the configuration session. No —Exits the configuration session without committing the configuration changes. Cancel —Remains in the configuration session, without committing the configuration changes.

Enabling BFD Sessions on Bundle Members

To enable BFD sessions on bundle member links, complete these steps:

Procedure

	Command or Action	Purpose
Step 1	configure Example: `RP/0/RP0/CPU0:router# configure`	Enters mode.
Step 2	interface Bundle-Ether `bundle-id` Example: `RP/0/RP0/CPU0:router(config)# interface Bundle-Ether 1`	Enters interface configuration mode for the specified bundle ID.
Step 3	bfd address-family ipv4 fast-detect Example: `RP/0/RP0/CPU0:router(config-if)# bfd address-family ipv4 fast-detect`	Enables IPv4 BFD sessions on bundle member links.
Step 4	bfd mode ietf Example: `RP/0/RP0/CPU0:router(config-if)# bfd mode ietf`	Enables IETF mode for BFD over bundle for the specified bundle.
Step 5	Use the commit or end command.	commit —Saves the configuration changes and remains within the configuration session. end —Prompts user to take one of these actions: Yes — Saves configuration changes and exits the configuration session. No —Exits the configuration session without committing the configuration changes. Cancel —Remains in the configuration session, without committing the configuration changes.

Specifying the BFD Destination Address on a Bundle

To specify the BFD destination address on a bundle, complete these steps:

Procedure

	Command or Action	Purpose
Step 1	configure Example: `RP/0/RP0/CPU0:router# configure`	Enters mode.
Step 2	interface Bundle-Ether `bundle-id` Example: `RP/0/RP0/CPU0:router(config)# interface Bundle-Ether 1`	Enters interface configuration mode for the specified bundle ID.
Step 3	bfd address-family ipv4 destination `ip-address` Example: `RP/0/RP0/CPU0:router(config-if)# bfd address-family ipv4 destination 10.20.20.1`	Specifies the primary IPv4 address assigned to the bundle interface on a connected remote system, where `ip-address` is the 32-bit IP address in dotted-decimal format (A.B.C.D).
Step 4	Use the commit or end command.	commit —Saves the configuration changes and remains within the configuration session. end —Prompts user to take one of these actions: Yes — Saves configuration changes and exits the configuration session. No —Exits the configuration session without committing the configuration changes. Cancel —Remains in the configuration session, without committing the configuration changes.

Configuring the Minimum Thresholds for Maintaining an Active Bundle

The bundle manager uses two configurable minimum thresholds to determine whether a bundle can be brought up or remain up, or is down, based on the state of its member links.

Minimum active number of links
Minimum active bandwidth available

Whenever the state of a member changes, the bundle manager determines whether the number of active members or available bandwidth is less than the minimum. If so, then the bundle is placed, or remains, in DOWN state. Once the number of active links or available bandwidth reaches one of the minimum thresholds, then the bundle returns to the UP state.

To configure minimum bundle thresholds, complete these steps:

Procedure

Command or Action Purpose

Step 1

configure

Example:


RP/0/RP0/CPU0:router# configure

Enters mode.

Step 2

interface Bundle-Ether bundle-id

Example:


RP/0/RP0/CPU0:router(config)# interface Bundle-Ether 1

Enters interface configuration mode for the specified bundle ID.

Step 3

bundle minimum-active bandwidth kbps

Example:


RP/0/RP0/CPU0:router(config-if)# bundle minimum-active bandwidth 580000

Sets the minimum amount of bandwidth required before a bundle can be brought up or remain up. The range is from 1 through a number that varies depending on the platform and the bundle type.

Step 4

bundle minimum-active links links

Example:


RP/0/RP0/CPU0:router(config-if)# bundle minimum-active links 2

Sets the number of active links required before a bundle can be brought up or remain up. The range is from 1 to 32.

Note

When BFD is started on a bundle that is already active, the BFD state of the bundle is declared when the BFD state of all the existing active members is known.

Step 5

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

Yes — Saves configuration changes and exits the configuration session.
No —Exits the configuration session without committing the configuration changes.
Cancel —Remains in the configuration session, without committing the configuration changes.

Configuring BFD Packet Transmission Intervals and Failure Detection Times on a Bundle

BFD asynchronous packet intervals and failure detection times for BFD sessions on bundle member links are configured using a combination of the bfd address-family ipv4 minimum-interval and bfd address-family ipv4 multiplier interface configuration commands on a bundle.

The BFD control packet interval is configured directly using the bfd address-family ipv4 minimum-interval command. The failure detection times are determined by a combination of the interval and multiplier values in these commands.

To configure the minimum transmission interval and failure detection times for BFD asynchronous mode control packets on bundle member links, complete these steps:

Procedure

Command or Action Purpose

Step 1

configure

Example:


RP/0/RP0/CPU0:router# configure

Enters mode.

Step 2

interface Bundle-Ether bundle-id

Example:


RP/0/RP0/CPU0:router(config)# interface Bundle-Ether 1

Enters interface configuration mode for the specified bundle ID.

Step 3

bfd address-family ipv4 minimum-interval milliseconds

Example:


RP/0/RP0/CPU0:router(config-if)#bfd address-family ipv4 minimum-interval 2000

Note

Specifies the minimum interval, in milliseconds, for asynchronous mode control packets on IPv4 BFD sessions on bundle member links. The range is from 4 to 30000.

Step 4

bfd address-family ipv4 multiplier multiplier

Example:


RP/0/RP0/CPU0:router(config-if)#bfd address-family ipv4 multiplier 30

Specifies a number that is used as a multiplier with the minimum interval to determine BFD control packet failure detection times and transmission intervals for IPv4 BFD sessions on bundle member links. The range is from 2 to 50. The default is 3.

Note

Although the command allows you to configure a minimum of 2, the supported minimum is 3.

Step 5

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

Yes — Saves configuration changes and exits the configuration session.
No —Exits the configuration session without committing the configuration changes.
Cancel —Remains in the configuration session, without committing the configuration changes.

Configuring BFD over Bundle per Member Mode

Procedure

Command or Action Purpose

Step 1

configure

Example:


RP/0/RP0/CPU0:router# configure

Enters mode.

Step 2

bfd bundle per-member mode ietf

Example:


RP/0/RP0/CPU0:router(config)# bfd bundle per-member mode ietf

Enables IETF mode for BFD over per-bundle member link.

Step 3

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

Yes — Saves configuration changes and exits the configuration session.
No —Exits the configuration session without committing the configuration changes.
Cancel —Remains in the configuration session, without committing the configuration changes.

Configure BFD over Bundles IETF Mode Support on a Per Bundle Basis

To configure BFD over Bundles IETF mode support on a per bundle basis use these steps:

Procedure

	Command or Action	Purpose
Step 1	configure Example: `RP/0/RP0/CPU0:router# configure`	Enters mode.
Step 2	interface Bundle-Ether `bundle-id` Example: `RP/0/RP0/CPU0:router(config)# interface Bundle-Ether 1`	Enters interface configuration mode for the specified bundle ID.
Step 3	bfd mode ietf Example: `RP/0/RP0/CPU0:router(config-if)# bfd mode ietf`	Enables IETF mode for BFD over bundle for the specified bundle.
Step 4	bfd address-family ipv4 fast-detect Example: `RP/0/RP0/CPU0:router(config-if)# bfd address-family ipv4 fast-detect`	Enables IPv4 BFD sessions on the specified bundle.
Step 5	Use the commit or end command.	commit —Saves the configuration changes and remains within the configuration session. end —Prompts user to take one of these actions: Yes — Saves configuration changes and exits the configuration session. No —Exits the configuration session without committing the configuration changes. Cancel —Remains in the configuration session, without committing the configuration changes.
Step 6	show bundle bundle-ether `bundle-id`	Displays the selected bundle mode.

BFD over Bundle with IPv4 Unnumbered Interfaces

BFD over Bundle with IPv4 Unnumbered Interfaces feature enables BFD to run on IP unnumbered interfaces, which take the IP address from the loopback address. The same loopback address is used on multiple interfaces. This saves IP addresses space or range.

BFD creates a session on the unnumbered interface for which the BFD clients provide the source and destination IP address along with the interface index. BFD establishes the session on the Layer 3 unnumbered link to which the interface index corresponds. The source address is derived from the Loopback interface at the source. The destination node also uses IP unnumbered interface with loopback address and that is used as destination IP address.

BFD sends control packets to the unnumbered interfaces. These control packets are the regular IP BFD packets. Address Resolution Protocol (ARP) resolves the destination loopback IP address to the destination node’s router MAC address.

Restriction

Only Asynchronous mode is supported.

Configure BFD over Bundle with IPv4 Unnumbered Interface

Configure loopback address
Add physical interface to bundle
Configure BOB session on an unnumbered interface

Configure Loopback Address

Router(config)# interface loopback 1
Router(config-if)# ipv4 address 10.1.1.1 255.255.255.0

Add Physical Interface to Bundle

Router(config)# interface HundredGigE0/0/1/0
Router(config-if)# bundle id 1 mode on

Configure a BFD over Bundle Session on an Unnumbered Interface

Router(config)# interface Bundle-Ether1
Router(config-if)# bfd address-family ipv4 destination 10.2.2.2
Router(config-if)# bfd address-family ipv4 fast-detect
Router(config-if)# ipv4 point-to-point
Router(config-if)# ipv4 unnumbered Loopback1
Router(config-if)# lldp
Router(config-if)# enable

Running Configuration


interface Loopback1
ipv4 address 10.1.1.1 255.255.255.0
!
interface HundredGigE0/0/1/0
bundle id 1 mode on
!
interface Bundle-Ether1
bfd address-family ipv4 destination 10.2.2.2
bfd address-family ipv4 fast-detect
ipv4 point-to-point
ipv4 unnumbered Loopback1
lldp
 enable

Coexistence Between BFD over Bundle and BFD over Logical Bundle

The coexistence between BFD over Bundle (BoB) and BFD over Logical Bundle (BLB) feature allows you to monitor either physical bundle member for BOB, or logical interface for BLB, or both. This feature enables BFD to converge fast.

Configuration Example

Configure one or more linecards to allow hosting of MP BFD sessions. If no linecards are included, linecards groups are not formed, and consequently no BFD MP sessions are created. For default settings of group size and number, you must add at least two lines with the bfd multiple-paths include location node-id command and valid line cards to the configuration for the algorithm to start forming groups and BFD MP sessions to be established.

Router(config)# bfd multipath include location 0/RP0/CPU0
Router(config)# bfd multipath include location 0/1/CPU0

/* Configure inherited coexistence mode */
Router(config)# bfd
Router(config-bfd)# bundle coexistence bob-blb inherit

/* Configure logical coexistence mode */
Router(config)# bfd
Router(config-bfd)# bundle coexistence bob-blb logical

Running Configuration

Running confiiguration for inherited coexistence:

bfd
bundle coexistence bob-blb inherit

Running confiiguration for logical mode:

bfd
bundle coexistence bob-blb logical

Verification

Verify BOB and BLB coexistence inherited mode.

Router# show bfd session                                                
Mon May 31 02:55:44.584 UTC
Interface           Dest Addr           Local det time(int*mult)      State     
                                    Echo             Async   H/W   NPU     
------------------- --------------- ---------------- ---------------- ----------
Te0/0/0/7           33.33.33.2      0s(0s*0)         450ms(150ms*3)   UP    
                                                             Yes   0/RP0/CPU0       
BE123               33.33.33.2      n/a              n/a              UP        
                                                             No    n/a            
BE123.1             34.34.34.2      n/a              n/a              UP        
                                                             No    n/a

Router# show bfd session interface bundle-ether 123 detail   
Fri May 28 13:49:35.268 UTC
I/f: Bundle-Ether123, Location: 0/RP0/CPU0
Dest: 33.33.33.2
Src: 33.33.33.1
 State: UP for 0d:0h:29m:50s, number of times UP: 1
 Session type: PR/V4/SH/BI/IB
Session owner information:
                            Desired               Adjusted
  Client               Interval   Multiplier Interval   Multiplier
  -------------------- --------------------- ---------------------
  bundlemgr_distrib    150 ms     3          150 ms     3         
Session association information:
  Interface            Dest Addr / Type                   
  -------------------- -----------------------------------
  Te0/0/0/7            33.33.33.2                              
                       BFD_SESSION_SUBTYPE_RTR_BUNDLE_MEMBER   
  BE123.1              34.34.34.2                              
                       BFD_SESSION_SUBTYPE_STATE_INHERIT

Router# show bfd session interface bundle-ether 123.1 detail 
Fri May 28 13:49:59.316 UTC
I/f: Bundle-Ether123.1, Location: 0/RP0/CPU0
Dest: 34.34.34.2
Src: 34.34.34.1
 State: UP for 0d:0h:12m:54s, number of times UP: 1
 Session type: PR/V4/SH/IH
Session owner information:
                            Desired               Adjusted
  Client               Interval   Multiplier Interval   Multiplier
  -------------------- --------------------- ---------------------
  ipv4_static          100 ms     3          100 ms     3         
Session association information:
  Interface            Dest Addr / Type                   
  -------------------- -----------------------------------
  BE123                33.33.33.2                              
                       BFD_SESSION_SUBTYPE_RTR_BUNDLE_INTERFACE

Router# show bfd session interface tenGigE 0/0/0/7 detail 
Mon May 31 03:00:04.635 UTC
I/f: TenGigE0/0/0/7, Location: 0/0/CPU0
Dest: 33.33.33.2
Src: 33.33.33.1
 State: UP for 2d:13h:40m:19s, number of times UP: 1
 Session type: PR/V4/SH/BM/IB
Received parameters:
 Version: 1, desired tx interval: 150 ms, required rx interval: 150 ms
 Required echo rx interval: 0 ms, multiplier: 3, diag: None
 My discr: 2147493276, your discr: 2147492184, state UP, D/F/P/C/A: 0/0/0/1/0
Transmitted parameters:
 Version: 1, desired tx interval: 150 ms, required rx interval: 150 ms
 Required echo rx interval: 0 ms, multiplier: 3, diag: None
 My discr: 2147492184, your discr: 2147493276, state UP, D/F/P/C/A: 0/0/0/1/0
Timer Values:
 Local negotiated async tx interval: 150 ms
 Remote negotiated async tx interval: 150 ms
 Desired echo tx interval: 0 s, local negotiated echo tx interval: 0 ms
 Echo detection time: 0 ms(0 ms*3), async detection time: 450 ms(150 ms*3)
Local Stats:
 Intervals between async packets:
   Tx: Number of intervals=4, min=5 ms, max=15 s, avg=6927 ms
       Last packet transmitted 222007 s ago
   Rx: Number of intervals=15, min=3 ms, max=1700 ms, avg=1133 ms
       Last packet received 222018 s ago
 Intervals between echo packets:
   Tx: Number of intervals=0, min=0 s, max=0 s, avg=0 s
       Last packet transmitted 0 s ago
   Rx: Number of intervals=0, min=0 s, max=0 s, avg=0 s
       Last packet received 0 s ago
 Latency of echo packets (time between tx and rx):
   Number of packets: 0, min=0 ms, max=0 ms, avg=0 ms
Session owner information:
                            Desired               Adjusted
  Client               Interval   Multiplier Interval   Multiplier
  -------------------- --------------------- ---------------------
  bundlemgr_distrib    150 ms     3          150 ms     3         
Session association information:
  Interface            Dest Addr / Type                   
  -------------------- -----------------------------------
  BE123                33.33.33.2                              
                       BFD_SESSION_SUBTYPE_RTR_BUNDLE_INTERFACE

H/W Offload Info:
 H/W Offload capability : Y, Hosted NPU     : 0/RP0/CPU0
 Async Offloaded        : Y, Echo Offloaded : N
 Async rx/tx            : 122/51 

Platform Info:
NPU ID: 0 
Async RTC ID        : 1          Echo RTC ID        : 0
Async Feature Mask  : 0x0        Echo Feature Mask  : 0x0
Async Session ID    : 0x2158     Echo Session ID    : 0x0
Async Tx Key        : 0x80002158  Echo Tx Key        : 0x0
Async Tx Stats addr : 0x0   Echo Tx Stats addr : 0x0
Async Rx Stats addr : 0x0   Echo Rx Stats addr : 0x0

Verify BOB and BLB coexistence logical mode.

show bfd session
Mon May 31 02:54:07.442 UTC
Interface           Dest Addr           Local det time(int*mult)      State     
                                    Echo             Async   H/W   NPU     
------------------- --------------- ---------------- ---------------- ----------
Te0/0/0/7           33.33.33.2      0s(0s*0)         450ms(150ms*3)   UP        
                                                             Yes   0/0/CPU0       
BE123.1             34.34.34.2      0s(0s*0)         300ms(100ms*3)   UP        
                                                             Yes   0/0/CPU0       
BE123               33.33.33.2      n/a              n/a              UP        
                                                             No    n/a

Router# show bfd session interface bundle-ether 123 detail                        
Fri May 28 14:04:41.331 UTC
I/f: Bundle-Ether123, Location: 0/RP0/CPU0
Dest: 33.33.33.2
Src: 33.33.33.1
 State: UP for 0d:0h:44m:56s, number of times UP: 1
 Session type: PR/V4/SH/BI/IB
Session owner information:
                            Desired               Adjusted
  Client               Interval   Multiplier Interval   Multiplier
  -------------------- --------------------- ---------------------
  bundlemgr_distrib    150 ms     3          150 ms     3         
Session association information:
  Interface            Dest Addr / Type                   
  -------------------- -----------------------------------
  Te0/0/0/7            33.33.33.2                              
                       BFD_SESSION_SUBTYPE_RTR_BUNDLE_MEMBER

Router# show bfd session interface tenGigE 0/0/0/7 detail 
Mon May 31 03:04:25.714 UTC
I/f: TenGigE0/0/0/7, Location: 0/RP0/CPU0Dest: 33.33.33.2
Src: 33.33.33.1
 State: UP for 2d:13h:44m:40s, number of times UP: 1
 Session type: PR/V4/SH/BM/IB
Received parameters:
 Version: 1, desired tx interval: 150 ms, required rx interval: 150 ms
 Required echo rx interval: 0 ms, multiplier: 3, diag: None
 My discr: 2147493276, your discr: 2147492184, state UP, D/F/P/C/A: 0/0/0/1/0
Transmitted parameters:
 Version: 1, desired tx interval: 150 ms, required rx interval: 150 ms
 Required echo rx interval: 0 ms, multiplier: 3, diag: None
 My discr: 2147492184, your discr: 2147493276, state UP, D/F/P/C/A: 0/0/0/1/0
Timer Values:
 Local negotiated async tx interval: 150 ms
 Remote negotiated async tx interval: 150 ms
 Desired echo tx interval: 0 s, local negotiated echo tx interval: 0 ms
 Echo detection time: 0 ms(0 ms*3), async detection time: 450 ms(150 ms*3)
Local Stats:
 Intervals between async packets:
   Tx: Number of intervals=4, min=5 ms, max=15 s, avg=6927 ms
       Last packet transmitted 222268 s ago
   Rx: Number of intervals=15, min=3 ms, max=1700 ms, avg=1133 ms
       Last packet received 222279 s ago
 Intervals between echo packets:
   Tx: Number of intervals=0, min=0 s, max=0 s, avg=0 s
       Last packet transmitted 0 s ago
   Rx: Number of intervals=0, min=0 s, max=0 s, avg=0 s
       Last packet received 0 s ago
 Latency of echo packets (time between tx and rx):
   Number of packets: 0, min=0 ms, max=0 ms, avg=0 ms
Session owner information:
                            Desired               Adjusted
  Client               Interval   Multiplier Interval   Multiplier
  -------------------- --------------------- ---------------------
  bundlemgr_distrib    150 ms     3          150 ms     3         
Session association information:
  Interface            Dest Addr / Type                   
  -------------------- -----------------------------------
  BE123                33.33.33.2                              
                       BFD_SESSION_SUBTYPE_RTR_BUNDLE_INTERFACE

H/W Offload Info:
 H/W Offload capability : Y, Hosted NPU     : 0/RP0/CPU0
 Async Offloaded        : Y, Echo Offloaded : N
 Async rx/tx            : 122/51 

Platform Info:
NPU ID: 0 
Async RTC ID        : 1          Echo RTC ID        : 0
Async Feature Mask  : 0x0        Echo Feature Mask  : 0x0
Async Session ID    : 0x2158     Echo Session ID    : 0x0
Async Tx Key        : 0x80002158  Echo Tx Key        : 0x0
Async Tx Stats addr : 0x0   Echo Tx Stats addr : 0x0
Async Rx Stats addr : 0x0   Echo Rx Stats addr : 0x0

Router# show bfd session interface bundle-ether 123.1 detail                      
Fri May 28 14:04:46.893 UTC
I/f: Bundle-Ether123.1, Location: 0/0/CPU0
Dest: 34.34.34.2
Src: 34.34.34.1
 State: UP for 0d:0h:5m:18s, number of times UP: 1
 Session type: SW/V4/SH/BL
Received parameters:
 Version: 1, desired tx interval: 100 ms, required rx interval: 100 ms
 Required echo rx interval: 0 ms, multiplier: 3, diag: None
 My discr: 984, your discr: 124, state UP, D/F/P/C/A: 0/0/0/1/0
Transmitted parameters:
 Version: 1, desired tx interval: 100 ms, required rx interval: 100 ms
 Required echo rx interval: 0 ms, multiplier: 3, diag: None
 My discr: 124, your discr: 984, state UP, D/F/P/C/A: 0/1/0/1/0
Timer Values:
 Local negotiated async tx interval: 100 ms
 Remote negotiated async tx interval: 100 ms
 Desired echo tx interval: 0 s, local negotiated echo tx interval: 0 ms
 Echo detection time: 0 ms(0 ms*3), async detection time: 300 ms(100 ms*3)
Label:
 Internal label: 24000/0x5dc0
Local Stats:
 Intervals between async packets:
   Tx: Number of intervals=3, min=103 ms, max=19 s, avg=7023 ms
       Last packet transmitted 318 s ago
   Rx: Number of intervals=15, min=1 ms, max=1704 ms, avg=1315 ms
       Last packet received 318 s ago
 Intervals between echo packets:
   Tx: Number of intervals=0, min=0 s, max=0 s, avg=0 s
       Last packet transmitted 0 s ago
   Rx: Number of intervals=0, min=0 s, max=0 s, avg=0 s
       Last packet received 0 s ago
 Latency of echo packets (time between tx and rx):
   Number of packets: 0, min=0 ms, max=0 ms, avg=0 ms
MP download state: BFD_MP_DOWNLOAD_ACK
State change time: May 28 13:59:07.124
Session owner information:
                            Desired               Adjusted
  Client               Interval   Multiplier Interval   Multiplier
  -------------------- --------------------- ---------------------
  ipv4_static          100 ms     3          100 ms     3         

H/W Offload Info:
 H/W Offload capability : Y, Hosted NPU     : 0/0/CPU0
 Async Offloaded        : Y, Echo Offloaded : N
 Async rx/tx            : 16/4 

Platform Info:
NPU ID: 0 
Async RTC ID        : 1          Echo RTC ID        : 0
Async Feature Mask  : 0x0        Echo Feature Mask  : 0x0
Async Session ID    : 0x7c       Echo Session ID    : 0x0
Async Tx Key        : 0x7c  Echo Tx Key        : 0x0
Async Tx Stats addr : 0x0   Echo Tx Stats addr : 0x0
Async Rx Stats addr : 0x0   Echo Rx Stats addr : 0x0

Seamless Bidirectional Forwarding Detection

Table 3. Feature History Table
Feature Name	Release Information	Feature Description
Seamless Bidirectional Forwarding Detection	Release 24.2.11	This feature now extends support on the Cisco NCS 540 Series routers running on Cisco IOS XR7.
Seamless Bidirectional Forwarding Detection	Release 24.2.1	Introduced in this release on the following Cisco NCS 540 router variants running on Cisco IOS XR: N540-ACC-SYS N540X-ACC-SYS N540-24Z8Q2C-SYS This feature introduces support for NCS 5500 routers as a Seamless BFD (S-BFD) reflector. Seamless BFD simplifies the negotiation and state establishment aspects of BFD by predetermining session discriminators and maintaining session state only at the headend. This approach ensures quicker connectivity tests and reduces complexity in session establishment. Previously, support for Seamless BFD reflector was not available. The feature introduces these changes: CLI: This feature introduces the sbfd command.

Advantages of SBFD over BFD

Seamless Bidirectional Forwarding Detection (S-BFD), is a simplified mechanism for using BFD with a large proportion of negotiation aspects eliminated, thus providing benefits such as quick provisioning, as well as improved control and flexibility for network nodes initiating path monitoring.

Components of S-BFD

S-BFD includes the following components:

S-BFD discriminator
Reflector BFD session
S-BFD initiator

Each network node allocates one or more S-BFD discriminators for local entities and creates a reflector BFD session. The S-BFD initiator sends S-BFD control packets with the corresponding discriminator value. The reflector BFD session listens to incoming S-BFD control packets addressed to local entities and generates response S-BFD control packets.

Key differences between BFD and S-BFD

In BFD, each end of the connection maintains a BFD state and transmits packets periodically over a forwarding path. S-BFD is unidirectional, resulting in faster session activation than BFD. The BFD state and client context is maintained on the head-end (initiator) only. The tail-end (reflector) validates the BFD packet and responds, so there is no need to maintain the BFD state on the tail-end.

Initiator and Reflector Components of S-BFD

S-BFD runs in an asymmetric behavior, using initiators and reflectors.

The following figure represents the roles of the S-BFD initiator and reflector.

The initiator is an S-BFD session on a network node that performs a continuity test to a remote entity by sending S-BFD packets. The initiator injects the S-BFD packets into the segment-routing traffic-engineering (SRTE) policy. The initiator triggers the S-BFD session and maintains the BFD state and client context. For more information about configuring SRTE policies, see the Configure SR-TE Policies chapter in the Segment Routing Configuration Guide.

The S-BFD reflector is an S-BFD session on a network node that listens for incoming S-BFD control packets to local entities and generates response S-BFD control packets. The reflector is stateless and only reflects the S-BFD packets back to the initiator.

Role of Discriminators in S-BFD Control Packet

The BFD control packet carries 32-bit discriminators (local and remote) to demultiplex BFD sessions. S-BFD requires globally unique S-BFD discriminators that are known by the initiator.

The S-BFD control packets contain the discriminator of the initiator, which is created dynamically by the initiator, and the discriminator of the reflector, which is configured as a local discriminator on the reflector.

Usage Guidelines and Limitations for S-BFD

The following usage guidelines and limitations apply:

The NCS 5500 routers do not support initiator mode.
The feature support is only for a global VRF and IPv4 addresses.
The supported Packets Per Second (PPS) limit is up to 3000. Also, consider the jitter used by the initiator for accurate performance assessment.
The network administrator configures reflector node discriminators at the initiator, allowing the initiator to know the globally unique discriminators of the reflector before the session starts.

Configure the S-BFD Reflector

This section includes steps to configure the S-BFD reflector.

Before you begin

Each reflector should have at least one globally unique discriminator, to ensure the S-BFD packet arrives on the intended reflector.
An S-BFD reflector only accepts BFD control packets where "Your Discriminator" is the reflector discriminator.

Procedure

Step 1	Configure the local discriminators on the reflector using the sbfd local-discriminator {`ipv4-address` \| `32-bit-value` \| dynamic \| interface `interface` } command. You can configure a local discriminator in one of the following ways. For more information about configuring a local discriminator, see the local-discriminator command in the Segment Routing Command Reference for Cisco 5500 Series Routers. Configure an IPv4 address as the local discriminator. `Router(config)#sbfd Router(config-sbfd)#local-discriminator 192.0.2.1` Configure a unique 32-bit value as the local discriminator. `Router(config)#sbfd Router(config-sbfd)#local-discriminator 987654321` Configure an IPv4 address of the interface as the local discriminator. `Router(config)#sbfd Router(config-sbfd)#local-discriminator interface Loopback0` Configure a randomly generated value as the local discriminator. `Router(config)#sbfd Router(config-sbfd)#local-discriminator dynamic`
Step 2	Verify the configuration using the show running-config command. Example: `local-discriminator 10.1.1.5 local-discriminator 987654321 local-discriminator dynamic local-discriminator interface Loopback0 !`
Step 3	Verify the configured BFD local discriminators using the show bfd target-identifier command. Example: `Router#show bfd target-identifier local Local Target Identifier Table ----------------------------- Discr Discr Src VRF Status Flags Name ----- --------- ------- -------- -------- 16843013 Local default enable -----ia- 987654321 Local default enable ----v--- 2147483649 Local default enable -------d Legend: TID - Target Identifier a - IP Address mode d - Dynamic mode i - Interface mode v - Explicit Value mode`
Step 4	Verify the S-BFD reflector configuration using the show bfd reflector command. Example: Router#show bfd reflector info detail location 0/0/CPU0 Local Discr : 2147483649 Remote Discr : 65576 Source Address : 1.1.1.1 Last DOWN received Time : (NA) Last Rx packets timestamps before DOWN [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] Last Tx packets timestamps before DOWN [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] [NA ] Last UP sent Time : (Jun 7 14:59:34.763) Last recent Rx packets timestamps: [Jun 7 15:00:18.653 ] [Jun 7 15:00:18.751 ] [Jun 7 15:00:18.837 ] [Jun 7 15:00:18.927 ] [Jun 7 15:00:18.085 ] [Jun 7 15:00:18.185 ] [Jun 7 15:00:18.274 ] [Jun 7 15:00:18.372 ] [Jun 7 15:00:18.464 ] [Jun 7 15:00:18.562 ] Last recent Tx packets timestamps: [Jun 7 15:00:18.653 ] [Jun 7 15:00:18.751 ] [Jun 7 15:00:18.837 ] [Jun 7 15:00:18.927 ] [Jun 7 15:00:18.085 ] [Jun 7 15:00:18.185 ] [Jun 7 15:00:18.274 ] [Jun 7 15:00:18.372 ] [Jun 7 15:00:18.464 ] [Jun 7 15:00:18.563 ]

BFD Transparency

Bidirectional Forwarding Detection(BFD) protocol is a simple hello mechanism that detects failures in a network in less than one second, depending on the timer value configured.

Both endpoints of a BFD Session periodically send Hello packets to each other. If a number of those packets are not received, the session is considered down. BFD provides fast BFD peer failure detection times independently of all media types, encapsulations, topologies, and routing protocols BGP, IS-IS, and OSPF.

BFD Transparency feature enables you to configure BFD Sessions between customer edge devices connected over an L2VPN network. These BFD sessions are transparent to the core. For example, BFD packets being exchanged between CEs are neither dropped on any router in the core, nor punted on any core device.

In this section, you will learn how to configure BFD Transparency in Ethernet VPN (EVPN) Virtual Private Wire Service (VPWS).

Ethernet VPN Virtual Private Wire Service

EVPN VPWS (Ethernet VPN Virtual Private Wire Service) is a BGP control plane solution for point-to-point services. It implements signaling and encapsulation techniques for establishing an EVPN instance between a pair of provider edge devices.

EVPN VPWS supports both single-homing and multi-homing.

Configuration

The following sections describes the procedure for configuring IP Fast Reroute with Remote LFA.

Configure L2VPN on the provide edge router
Configure BFD on the customer edge router

Configure L2VPN on the Provide Edge Router


/* Enable IS-IS and configure routing level for an area. */
RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# interface tengige 0/0/0/2.1
RP/0/RP0/CPU0:router(config-subif)# exit
RP/0/RP0/CPU0:router(config)# router isis
RP/0/RP0/CPU0:router(config-isis)# is-type level-2-only
RP/0/RP0/CPU0:router(config-isis)# net 49.1234.2222.2222.2222.00
RP/0/RP0/CPU0:router(config-isis)# nsr
RP/0/RP0/CPU0:router(config-isis)# nsf cisco
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-isis-af)# metric style wide
RP/0/RP0/CPU0:router(config-isis)# end
RP/0/RP0/CPU0:router(config)# interface Bundle-Ether 199
RP/0/RP0/CPU0:router(config-if)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-if)# end
RP/0/RP0/CPU0:router(config)# interface Loopback 0
RP/0/RP0/CPU0:router(config-if)# end
RP/0/RP0/CPU0:router(config-if)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-if)# exit

/* Configure L2VPN EVPN address family. */
RP/0/RP0/CPU0:router(config)# router bgp 100
RP/0/RP0/CPU0:router(config-bgp)# bgp router-id 10.10.10.1
RP/0/RP0/CPU0:router(config-bgp)# address-family l2vpn evpn
RP/0/RP0/CPU0:router(config-bgp)# neighbor 192.0.2.1
RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 100
RP/0/RP0/CPU0:router(config-bgp-nbr)# update-source Loopback 0
RP/0/RP0/CPU0:router(config-bgp-nbr)# address-family l2vpn evpn

/* Configure MPLS LDP for the physical core interface. */
RP/0/RP0/CPU0:router(config-bgp-nbr-af)# mpls ldp
RP/0/RP0/CPU0:router(config-bgp-nbr-af)# exit
RP/0/RP0/CPU0:router(config-bgp-nbr)# exit
RP/0/RP0/CPU0:router(config-bgp)# exit
RP/0/RP0/CPU0:router(config)# interface Bundle-Ether 199
RP/0/RP0/CPU0:router(config-if)# exit

/* Configure L2VPN Xconnect. */ 
RP/0/RP0/CPU0:router(config)# l2vpn 
RP/0/RP0/CPU0:router(config-l2vpn)# router-id 10.10.10.1 
RP/0/RP0/CPU0:router(config-l2vpn)# xconnect group bfdtr
RP/0/RP0/CPU0:router(config-l2vpn-xc)# p2p vpws-ce
RP/0/RP0/CPU0:router(config-l2vpn-xc-p2p)# interface TenGigE 0/0/0/1.1
RP/0/RP0/CPU0:ios(config-l2vpn-xc-p2p)# neighbor evpn evi 100 target 3 source 4

Configure BFD on the Customer Edge Router


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)#  router bgp 100
RP/0/RP0/CPU0:router(config-bgp)# bgp router-id 10.10.10.1
RP/0/RP0/CPU0:router(config-bgp)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-bgp-af)# exit
RP/0/RP0/CPU0:router(config-bgp)# neighbor 172.16.0.1
RP/0/RP0/CPU0:router(config-bgp)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 100
RP/0/RP0/CPU0:router(config-bgp-nbr)# bfd fast-detect
RP/0/RP0/CPU0:router(config-bgp-nbr)# bfd multiplier 2
RP/0/RP0/CPU0:router(config-bgp-nbr)# bfd minimum-interval 100
RP/0/RP0/CPU0:router(config-bgp-nbr)# update-source TenGigE 0/0/0/16.1
RP/0/RP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-bgp-nbr-af)#

Running Configuration

This section shows the BFD Transparency configuration.


!
interface TenGigE 0/0/0/1.1
  l2transport
router isis 1
   is-type level-2-only
   net 49.0000.1000.0000.0001.00
   nsr
   nsf cisco
   address-family ipv4 unicast
    metric-style wide
! 
  interface Bundle-Ether199
     address-family ipv4 unicast
  interface Loopback0
      address-family ipv4 unicast
router bgp 100
  bgp router-id 10.10.10.1
   address-family l2vpn evpn
    neighbor 192.0.2.1
     remote-as 100
     update-source Loopback 0
    address-family l2vpn evpn
 !   
   mpls ldp
   interface Bundle-Ether199
 !
  l2vpn
   router-id 10.10.10.1 
    xconnect group bfdtr
   p2p vpws-ce
    interface TenGigE 0/0/0/1.1
     neighbor evpn evi 100 target 3 source 4
 
         router bgp 100
          bgp router-id 10.10.10.1
           address-family ipv4 unicast
           !
           neighbor 172.16.0.1
            address-family ipv4 unicast
            remote-as 100
            bfd fast-detect
            bfd multiplier 2
            bfd minimum-interval 100
            update-source TenGigE0/0/0/16.1
            address-family ipv4 unicast

Verification

The show outputs given in the following section display the details of the configuration of the BFD transparency, and the status of their configuration.


/* Verify if the BFD session is up, and the timers are configured. */ 
RP/0/RP0/CPU0:router# show bfd session    

Thu Jan  4 03:07:15.529 UTC
Interface      Dest Addr  Local det time(int*mult)  State        Echo  Async   H/W      NPU     
-------------- ---------- ------------------------  --------     ----  -----   ---      ----
Te0/0/0/4.1    10.1.1.1   0s(0s*0)                  20ms(10ms*2) UP    Yes     0/RP0/CPU0                                                      Yes   0/RP0/CPU0


/* Verify if the BFD session is up and check the timer value, numbers of hellos exchanged, and information 
about last packet. */

RP/0/RP0/CPU0:router# show bfd session destination 10.1.1.1 detail
Thu Jan  4 03:09:48.573 UTC
I/f: TenGigE0/0/0/4.1, Location: 0/RP0/CPU0
Dest: 10.1.1.1
Src:  10.1.1.2
 State: UP for 0d:0h:9m:27s, number of times UP: 1
 Session type: PR/V4/SH
Received parameters:
 Version: 1, desired tx interval: 10 ms, required rx interval: 10 ms
Required echo rx interval: 0 ms, multiplier: 2, diag: None
 My discr: 2147483898, your discr: 2147483899, state UP, D/F/P/C/A: 0/0/0/1/0
Transmitted parameters:
 Version: 1, desired tx interval: 10 ms, required rx interval: 10 ms
 Required echo rx interval: 0 ms, multiplier: 2, diag: None
 My discr: 2147483899, your discr: 2147483898, state UP, D/F/P/C/A: 0/1/0/1/0
Timer Values:
 Local negotiated async tx interval: 10 ms
 Remote negotiated async tx interval: 10 ms
 Desired echo tx interval: 0 s, local negotiated echo tx interval: 0 ms
 Echo detection time: 0 ms(0 ms*2), async detection time: 20 ms(10 ms*2)
Local Stats:
 Intervals between async packets:
   Tx: Number of intervals=100, min=6 ms, max=6573 ms, avg=1506 ms
       Last packet transmitted 186 s ago
   Rx: Number of intervals=100, min=4 ms, max=5 s, avg=575 ms
       Last packet received 184 s ago
 Intervals between echo packets:
   Tx: Number of intervals=0, min=0 s, max=0 s, avg=0 s
       Last packet transmitted 0 s ago
   Rx: Number of intervals=0, min=0 s, max=0 s, avg=0 s
       Last packet received 0 s ago
 Latency of echo packets (time between tx and rx):
   Number of packets: 0, min=0 ms, max=0 ms, avg=0 ms
Session owner information:
                            Desired               Adjusted
  Client               Interval   Multiplier Interval   Multiplier
  -------------------- --------------------- ---------------------
  bgp-default          10 ms      2          10 ms      2         

H/W Offload Info:
 H/W Offload capability : Y, Hosted NPU     : 0/RP0/CPU0
 Async Offloaded        : Y, Echo Offloaded : N
 Async rx/tx            : 344/209 

Platform Info:
NPU ID: 0 
Async RTC ID        : 1          Echo RTC ID        : 0
Async Feature Mask  : 0x0        Echo Feature Mask  : 0x0
Async Session ID    : 0xfb       Echo Session ID    : 0x0
Async Tx Key        : 0x800000fb  Echo Tx Key        : 0x0
Async Tx Stats addr : 0x0   Echo Tx Stats addr : 0x0
Async Rx Stats addr : 0x0   Echo Rx Stats addr : 0x0

/* Verify the complete history including session state, type, transitions, offload history, last down reason if any,
 received and transmitted packets, rx/tx intervals, location, timestamp, and local and remote descriptors. */

RP/0/RP0/CPU0:router# show bfd session status history destination 10.1.10.1 location 0/RP0/CPU0  

Thu Jan  4 03:45:18.768 UTC
I/f: TenGigE0/0/0/4.10, Location: 0/RP0/CPU0 table_id:0xe0000000
State: UP, flags:0x80040
Iftype: 0x19, basecaps: 107
Async dest addr: 10.1.10.1
Async src addr: 10.1.10.2
Echo dest addr: 10.1.10.2
Echo src addr: 192.0.2.1
Additional info from Flags: 
 FIB is READY
 Session Active on 0/RP0/CPU0
Platform Info: 0x0, Mac Length: 18
Redundancy session info:
 Created from active BFD server
Last Down Diag: None
Last UP Time: Jan  4 03:00:19.272 

Received parameters:
 Version: 1, desired tx interval: 10 ms, required rx interval: 10 ms
 Required echo rx interval: 0 ms, multiplier: 2, diag: None
 My discr: 2147483747, your discr: 2147483751, state UP, D/F/P/C/A: 0/0/0/1/0

Transmitted parameters:
 Version: 1, desired tx interval: 10 ms, required rx interval: 10 ms
 Required echo rx interval: 0 ms, multiplier: 2, diag: None
 My discr: 2147483751, your discr: 2147483747, state UP, D/F/P/C/A: 0/1/0/1/0

Tx Echo pkt :
 Version: 0, Local Discr: 2147483751, Sequence No: 0

History:
[Jan  4 03:00:19.272] Session (v1) state change, triggered by event 'Remote
    state init', from INIT to UP with current diag being None
[Jan  4 03:00:16.851] Session (v1) state change, triggered by event 'Remote
    state down', from DOWN to INIT with current diag being None
[Jan  4 03:00:16.509] Session (v1) state change, triggered by event 'Session
    create', from Unknown to DOWN with current diag being None
[Jan  4 03:00:16.509] Flag cleared: session creation is in-progress, currently
    set flags (0x80040)

Offload history:
[Jan  4 03:06:42.013] Packet punted to sw: Packet word0 : (0x20c80218),
desired_min_tx_interval 10000, required_min_rx_interval 10000, Last punted pkt
    required_min_rx_interval 10000
[Jan  4 03:06:42.003] Packet punted to sw: Packet word0 : (0x20d80218),
desired_min_tx_interval 10000, required_min_rx_interval 10000, Last punted pkt
    required_min_rx_interval 10000
[Jan  4 03:06:41.989] Packet punted to sw: Packet word0 : (0x20c80218),
desired_min_tx_interval 10000, required_min_rx_interval 10000, Last punted pkt
    required_min_rx_interval 10000
[Jan  4 03:06:41.980] Packet punted to sw: Packet word0 : (0x20d80218),
desired_min_tx_interval 10000, required_min_rx_interval 10000, Last punted pkt
    required_min_rx_interval 10000
	
Rx Counters and Timestamps :
Async valid packets received: count 5280
  [Jan  4 03:06:42.013]  [Jan  4 03:06:42.003]  [Jan  4 03:06:41.989]
Async valid packets while session is not in Up state: count 3
  [Jan  4 03:00:19.272]  [Jan  4 03:00:18.030]  [Jan  4 03:00:16.851]

BFD Hardware Offload Support for IPv4

The Bidirectional Forwarding detection (BFD) Hardware Offload feature enables the offload of a BFD session to the network processing units of the line cards, in an IPv4 network. BFD hardware offload improves scale and reduces the overall network convergence time by sending rapid failure detection packets to the routing protocols for recalculating the routing table.

Restrictions

This feature is not supported over MPLS LDP interface and VRRP interface.
This feature is not supported over MPLS TE or RSVP tunnel.
BFD multihop will flap if underlay paths that consist of multiple bundle VLANs flap.

Confiugration Example

/* Configure BFD over Bundle(BOB) for hardware offload. */
Router# config
Router(config)# interface Bundle-Ether 1
Router(config-if)# bfd mode ietf
Router(config-if)# bfd address-family ipv4 multiplier 3
Router (config-if)# bfd address-family ipv4 destination 10.20.20.1
Router (config-if)# bfd address-family ipv4 fast-detect 
Router(config-if)# bfd address-family ipv4 minimum-interval 2000
Router(config-if)# ipv4 address 10.20.20.2/30

/* To define the line card to host BLB and BFD multihop sessions. */
Router(config)# bfd
Router(config-bfd)# 
multipath include location 0/RP0/CPU0

/* Configure BFD with a static route. */
Router(config)# router static
Router(config-static)# address-family ipv4 unicast 10.1.1.0/24 10.6.0.2 bfd fast-detect minimum-interval 350 multiplier 4

/* Configure BFD with IS-IS. */
Router(config)# router isis 65444
Router(config-isis)# address-family ipv4 unicast
Router(config-isis)# exit
Router(config-isis)# interface gigabitEthernet 0/3/0/1
Router(config-isis-if)#  bfd minimum-interval 6500
Router(config-isis-if)# bfd multiplier 7
Router(config-isis-if)# bfd fast-detect ipv4
Router(config-isis-if)# address-family ipv4 unicast

/* Configure BFDv4 with OSPF. */
Router(config)# router ospf main
Router(config-ospfv3)# area 0
Router(config-ospfv3-ar)#  interface gigabitEthernet 1/0/0/1
Router(config-ospfv3-ar-if)# bfd multiplier 7
Router(config-ospfv3-ar-if)# bfd fast-detect
Router(config-ospfv3-ar-if)# bfd minimum-interval 6500

/* Configuring BFD over BGP. */
Router(config)# router bgp 120
Router(config-bgp)# neighbor 10.6.6.1
Router(config-bgp-nbr)# bfd fast-detect
Router(config-bgp-nbr)# bfd multiplier 7
Router(config-bgp-nbr)# bfd minimum-interval 6500

Verification

Use the show bfd ipv4 session command to verify the configuration:

Router# show bfd ipv4 session
Interface           Dest Addr           Local det time(int*mult)       State     
                                    Echo             Async   H/W       NPU     
------------------- --------------- ---------------- ---------------- ----------
Hu0/0/0/22.93       10.20.20.1       0s(0s*0)         12ms(4ms*3)      UP        
                                                             Yes   0/RP0/CPU0

BFD Hardware Offload Support for IPv6

Table 4. Feature History
Feature Name	Release Information	Feature Description
BFD v6 - HW Offload and IPv6 BFD/BoB (Bundle over Bundle)	Release 7.3.1	The Bidirectional Forwarding detection (BFD) Hardware Offload feature enables the offload of a BFD session in an IPv6 network. With this feature, each bundle member link with IPv6 address runs its own BFD session This feature improves scale and reduces the overall network convergence time by sending rapid failure detection packets to the routing protocols for recalculating the routing table.

The Bidirectional Forwarding detection (BFD) Hardware Offload feature enables the offload of a BFD session to the network processing units of the line cards, in an IPv6 network. BFD hardware offload feature improves scale and reduces the overall network convergence time by sending rapid failure detection packets to the routing protocols for recalculating the routing table.

Restrictions

This feature is not supported over MPLS LDP interfaces.
This feature is not supported over MPLS TE or RSVP tunnel.
BFD Dampening is not supported for BFD over IPv6.
BFD over Bundle (BOB) over IPv6 is not supported with dynamically configured link-local address. It must be statically configured.
BFD multihop will flap if underlay paths that consist of multiple bundle VLANs flap.

Configuration Example

/* Configure BFD over Bundle(BOB) for hardware offload. */
Router# config
Router(config)# interface Bundle-Ether 1
Router(config-if)# bfd mode ietf
Router(config-if)# bfd address-family ipv6 multiplier 3
Router (config-if)# bfd address-family ipv6 destination 10.20:20::1
Router (config-if)# bfd address-family ipv6 fast-detect 
Router(config-if)# bfd address-family ipv6 minimum-interval 2000
Router(config-if)# ipv6 address 10:20:20::2/64

/* To define the line card to host BLB and BFD multihop sessions. */
Router(config)# bfd
Router(config-bfd)# multipath include location 0/RP0/CPU0

/* Configure BFD with a static route. */
Router(config)# router static
Router(config-static)# address-family ipv6 unicast 1011:17e4::1/128 ab11:15d2::2 bfd fast-detect minimum-interval 50 multiplier 3

/* Configure BFD with IS-IS. */
Router(config)# router isis 65444
Router(config-isis)# address-family ipv6 unicast
Router(config-isis)# exit
Router(config-isis)# interface gigabitEthernet 0/3/0/1
Router(config-isis-if)#  bfd minimum-interval 6500
Router(config-isis-if)# bfd multiplier 7
Router(config-isis-if)# bfd fast-detect ipv6
Router(config-isis-if)# address-family ipv6 unicast

/* Configure BFDv6 with OSPFv3. */
Router(config)# router ospfv3 main
Router(config-ospfv3)# area 0
Router(config-ospfv3-ar)#  interface gigabitEthernet 1/0/0/1
Router(config-ospfv3-ar-if)# bfd multiplier 7
Router(config-ospfv3-ar-if)# bfd fast-detect
Router(config-ospfv3-ar-if)# bfd minimum-interval 6500

/* Configuring BFD over BGP. */
Router(config)# router bgp 120
Router(config-bgp)# neighbor 2001:DB8:1::1
Router(config-bgp-nbr)# bfd fast-detect
Router(config-bgp-nbr)# bfd multiplier 7
Router(config-bgp-nbr)# bfd minimum-interval 6500

Verification

Use the show bfd ipv6 session command to verify the configuration:

Router# show bfd ipv6 session
Interface           Dest Addr      
                                        Local det time(int*mult)      State     
H/W                 NPU             Echo             Async           
------------------- --------------- ---------------- ---------------- ----------
BE7.2               fe80::28a:96ff:fed6:9cdb                      
Yes                 0/RP0/CPU0        0s(0s*0)         900ms(300ms*3)   UP        
BE7.4               fe80::28a:96ff:fed6:9cdb                      
Yes                 0/RP0/CPU0        0s(0s*0)         900ms(300ms*3)   UP

BFD Object Tracking

Object Tracking is enhanced to support BFD to track the reachability of remote IP addresses.This will enable complete detection and HSRP switch over to happen within a time of less than one second as BFD can perform the detection in the order of few milliseconds

Configuring BFD Object Tracking:

Procedure

	Command or Action	Purpose
Step 1	configure Example: `RP/0/RP0/CPU0:router# configure`	Enters mode.
Step 2	track `track-name` Example: `RP/0/RP0/CPU0:router(config)# track track1`	Enters track configuration mode. `track-name` —Specifies a name for the object to be tracked.
Step 3	type bfdrtr rate `tx-rate` Example: `RP/0/RP0/CPU0:router(config-track)# type bfdrtr rate 4`	tx_rate - time in msec at which the BFD should probe the remote entity
Step 4	debounce`debounce` Example: `RP/0/RP0/CPU0:router(config-if)# debounce 10`	debounce - count of consecutive BFD probes whose status should match before BFD notifies OT
Step 5	interface `if-name` Example: `RP/0/RP0/CPU0:router(config-track-line-prot)# interface GigabitEthernet0/0/0/4`	if_name - interface name on the source to be used by BFD to check the remote BFD status.
Step 6	destaddress `dest_addr` Example: `RP/0/RP0/CPU0:router(config-if)#destaddress 1.2.3.4`	dest_addr - IPV4 address of the remote BFD entity being tracked.
Step 7	Use the commit or end command.	commit —Saves the configuration changes and remains within the configuration session. end —Prompts user to take one of these actions: Yes — Saves configuration changes and exits the configuration session. No —Exits the configuration session without committing the configuration changes. Cancel —Remains in the configuration session, without committing the configuration changes.

IPv4 Multihop BFD

Table 5. Feature History Table
Feature Name	Release Information	Feature Description
Multihop BFD for IPv4 nondefault VRF	Release 7.7.1	BFD provides fast forwarding path failure detection between two routing devices that are connected by a network link. BFD Multihop enables you to detect connectivity between routers that span multiple network hops and follow unpredictable paths. Prior to this release, BFD Multihop was supported on default VRFs only. This feature provides you the flexibility to extend BFD Multihop for IPv4 non-default VRFs.

IPv4 Multihop BFD is a BFD session between two addresses between two nodes. An example of this feature is a BFD session between PE and CE loopback addresses or BFD sessions between routers that are several TTL hops away. The applications that support IPv4 Multihop BFD are external and internal BGP. IPv4 Multihop BFD feature supports BFD on arbitrary paths, which can span multiple networks hops.

A Virtual Routing and Forwarding (VRF) instance is a logical separation of a router's routing table. VRF allows you to have multiple routing tables on a single router, each with its own set of routes.

The default VRF is the first VRF that is created on a router. It is the VRF that is used by default for all routing protocols and interfaces.

Non-default VRFs must be explicitly configured.

The IPv4 Multihop BFD feature provides subsecond forwarding failure detection for a destination more than one hop, and up to 255 hops, away. IPv4 Multihop BFD feature is supported on all currently supported media-type for BFD single hop.

You can set up a BFD multihop session between a unique source-destination address pair that is provided by the client. You can set up a session two endpoints that have IP connectivity.

Multihop BFD over nondefault VRF feature runs on both default and non-default VRF.

Multihop BFD over nondefault VRF feature runs on IPv4 only.

Configure IPv4 Multihop BFD

This section describes how you can configure IPv4 Multihop BFD feature.


Router# configure
Router(config)# bfd
Router(config)# multipath include location 0/7/CPU0
Router(config)# router bgp 100
Router(config-bgp)# neighbor 209.165.200.225
Router(config-bgp-nbr)# remote-as 2000
Router(config-bgp-nbr)# update-source loopback 1
Router(config-bgp-nbr)# bfd fast-detect
Router(config-bgp-nbr)# bfd multiplier 3
Router(config-bgp-nbr)# bfd minimum-interval 300
Router(config-bgp-nbr)#address-family ipv4 unicast
Router(config-bgp-nbr-af)# route-policy pass-all in
Router(config-bgp-nbr-af)# route-policy pass-all out
Router(config-bgp-nbr-af)# commit

Running Configuration


bfd
 multipath include location 0/7/CPU0
router bgp 100
 neighbor 209.165.200.225
  remote-as 2000
  update-source loopback 1
  bfd fast-detect
  bfd multiplier 3
  bfd minimum-interval 300
address-family ipv4 unicast
      route-policy PASS-ALL in
    route-policy PASS-ALL out
  !
!

Verification

The show outputs given in the following section display the details of the configuration of the IPv4 Multihop BFD feature, and the status of their configuration.


Router# show tech-support bfdhwoff location 0/7/CPU0 file
harddisk: 
Tue Mar 20 11:20:29.214 PDT
++ Show tech start time: 2018-Mar-20.112029.PDT ++
Tue Mar 20 11:20:30 PDT 2018 Waiting for gathering to complete .............................
Tue Mar 20 11:22:37 PDT 2018 Compressing show tech output Show tech output available at 0/RP0/CPU0 :
/harddisk:/showtech-bfd-hwoff-platform-2018-Mar-20.112029.PDT.tgz
++ Show tech end time: 2018-Mar-20.112237.PDT ++

Configure Multihop BFD on IPv4 nondefault VRFs

Configure the following steps to configure Multihop BFD on IPv4 nondefault VRF:

Router(config)# router bgp 100
Router(config-bgp)# neighbor 209.165.200.225
Router(config-bgp-nbr)#vrf vrf1
Router(config-bgp-nbr-vrf)# exit
Router(config-bgp-nbr)# rd auto
Router(config-bgp-nbr)#address-family ipv4 unicast
Router(config-bgp-nbr-af)#redistribute connected
Router(config-bgp-nbr-af)# exit
Router(config-bgp)# neighbor 209.165.200.225 
Router(config-bgp-nbr)# remote-as 2000
Router(config-bgp-nbr)# bfd fast-detect
Router(config-bgp-nbr)# bfd multiplier 3
Router(config-bgp-nbr)# bfd minimum-interval 50
Router(config-bgp-nbr)# ebgp-multihop 255
Router(config-bgp-nbr)# update-source loopback 1
/* You can configure any interface here, including loopback or bvi */
Router(config-bgp-nbr)#address-family ipv4 unicast
Router(config-bgp-nbr-af)# route-policy pass-all in
Router(config-bgp-nbr-af)# route-policy pass-all out
Router(config-bgp-nbr-af)# commit

Running Configuration


router bgp 100
  neighbor 209.165.200.225
   vrf vrf1  
    exit
     rd auto
      address-family ipv4 unicast
       redistribute connected
        exit
         neighbor 209.165.200.225   
         remote-as 2000
         bfd fast-detect
         bfd multiplier 3
         bfd minimum-interval 50
         ebgp-multihop 255
         update-source loopback 1
          address-family ipv4 unicast
           route-policy pass-all in
           route-policy pass-all out

Verification


Router# show bfd session source 209.165.200.225 
Thu Mar 10 10:13:43.305 IST
Src Addr         Dest Addr    VRF Name         H/W NPU          
                               Local det time(int*mult)   State     
                              Echo    Async           
--------------   ---------   ------   ------ --------- ---------
209.165.200.225  192.0.2.254   vrf_1    Yes   0/0/CPU0     
                              n/a  150ms(50ms*3)          UP        
Router# show cef vrf vrf_1 209.165.200.225 location 0/0/CPU0
Thu Mar 10 10:24:13.372 IST
209.165.200.0/24, version 40, internal 0x5000001 0x30 (ptr 0x8ae26458) [1], 0x0 (0x0), 0xa08 (0x8dc144a8)
 Updated Mar  9 15:09:43.398
 Prefix Len 24, traffic index 0, precedence n/a, priority 3
LDI Update time Mar  9 14:59:28.284
   via 1.1.1.1/32, 605 dependencies, recursive [flags 0x6000]
    path-idx 0 NHID 0x0 [0x8dd35988 0x0]
    recursion-via-/32
    next hop VRF - 'default', table - 0xe0000000
    next hop 10.1.1.1/32 via 24015/0/21
    next hop 192.0.2.255/32 Te0/0/0/3.1  labels imposed {ImplNull 24162}

BFD over BVI

Table 6. Feature History
Feature Name	Release Information	Feature Description
BFD on BVI	Release 7.3.1	BFD can be configured on Bridge group Virtual Interface (BVI). BVI is a virtual interface within the router that acts like a normal routed interface that does not support bridging but represents the bridge group for the bridged physical interfaces. BFD detects the Layer3 fault over the BVI much quicker and informs the same to routing protocols.

In order for a VLAN to span a router, the router must be capable of forwarding frames from one interface to another, while maintaining the VLAN header. If the router is configured for routing a Layer 3 (network layer) protocol, it will terminate the VLAN and MAC layers at the interface on which a frame arrives. The MAC layer header can be maintained if the router bridges the network layer protocol. However, even regular bridging terminates the VLAN header.

Using the Integrated Routing Bridging (IRB) feature, a router can be configured for routing and bridging the same network layer protocol, on the same interface. This allows the VLAN header to be maintained on a frame while it transits a router from one interface to another. IRB provides the ability to route between a bridged domain and a routed domain with the Bridge Group Virtual Interface (BVI). The BVI is a virtual interface within the router that acts like a normal routed interface that does not support bridging, but represents the comparable bridge group to routed interfaces within the router. The interface number of the BVI is the number of the bridge group that the virtual interface represents. This number is the link between the BVI and the bridge group.

Because the BVI represents a bridge group as a routed interface, it must be configured only with Layer 3 (L3) characteristics, such as network layer addresses. Similarly, the interfaces configured for bridging a protocol must not be configured with any L3 characteristics.

BFD over IRB is a multipath single-hop session. In a BFD multipath session, BFD can be applied over virtual interfaces or between interfaces that are multihops away. The Cisco IOS XR Software BFD multihop is based on the RFC 5883—Bidirectional Forwarding Detection (BFD) for Multihop Paths. BFD over IRB is supported on IPv4 address, IPv6 global address, and IPv6 link-local address. The BFD over IRB is supported only in asynchronous mode and does not support echo mode.

Configuration Example


/* Configure a BVI interface and assign an IP address */
Router(config)# interface bvi 1
Router(config-if)# ipv4 address 192.168.1.1 255.255.255.0
Router(config-if)# exit

/* Configure the Layer 2 AC interface */
Router(config)# interface HundredGigE 0/0/1/3
Router(config-if)# l2transport
Router(config-if)# exit 

/* Configure OSPF as the routing protocol */
Router(config)# router ospf 100
Router(config-ospf)# router-id 192.168.1.1  
Router(config-ospf)# area 0
Router(config)# interface Loopback 100
Router(config)# exit

/* Configure BFD on BVI */
Router(config)# interface bvi1
Router(config-if)# bfd minimum-interval 50  
Router(config-if)# bfd fast-detect
Router(config-if)# bfd multiplier 3

/* Configure the line cards to allow hosting of Multipath BFD sessions. */
Router# configure
Router(config)# bfd multipath include location 0/RP0/CPU0

Running Configuration

interface BVI1
 ipv4 address 192.168.1.1 255.255.255.0
!
interface HundredGigE0/0/1/3
 l2transport
 !
!
router ospf 100
 router-id 192.168.1.1
 area 0
  interface Loopback100
  !
  interface BVI1
   bfd minimum-interval 50
   bfd fast-detect
   bfd multiplier 3
  !
 ! 
bfd multipath include location  0/RP0/CPU0       
!

   !

Multihop BFD over BVI

Table 7. Feature History Table
Feature Name	Release Information	Feature Description
Multihop BFD over Bridge Group Virtual Interface (BVI)	Release 7.4.1	The multihop BFD over Bridge Group Virtual Interface (BVI) feature introduces support for multihop BFD over (BVI). You can set up a multihop BFD session between two endpoints that have IP connectivity. This session is between a unique source-destination address pair that the client provides. This feature allows you to extend BFD on arbitrary paths. These arbitrary paths can span multiple network hops, hence detecting link failures.

Multihop BFD over BVI feature allows you to configure both routing and bridging on the same interface using Integrated Routing Bridging (IRB). IRB enables you to route between a bridged domain and a routed domain with the Bridge Group Virtual Interface (BVI).

The BVI is a virtual interface within the router that acts like a normal, routed interface that does not support bridging, but represents the comparable bridge group to routed interfaces within the router.

Restrictions

The minimum Multihop BFD timer for the BVI interface is 50 msec.
The multihop ttl-drop-threshold command is not supported.
The Multihop BFD over BVI or IRB functionality is supported only in asynchronous mode and does not support echo mode.
The Multihop BFD over BVI feature is not supported over MPLS and SR core.

Supported Functionality

This feature is supported in both IPv4 and IPv6.
BFD Multihop over BVI feature supports on client BGP.
BFD Multihop supports only over IP core.
BFD Multihop supports on all currently supported media-type for BFD single-hop.

Configuration


/* Configure a BVI interface and assign an IP address */
Router(config)# interface BVI1
Router(config-if)# host-routing
Router(config-if)# mtu 8986
Router(config-if)# ipv4 address 10.1.1.1 255.255.255.0
Router(config-if)# ipv6 address 10:1:1::1/120

/* Configure the Layer 2 AC interface */ 
Router(config-if)# interface TenGigE0/5/0/6/0.1 l2transport
Router(config-subif)# encapsulation dot1q 1
Router(config-subif)# rewrite ingress tag pop 1 symmetric

/* Configure L2VPN Bridge Domain */
Router(config-subif)# l2vpn 
Router(config-subif)# bridge group 1 
Router(config-subif)# bridge-domain 1 
Router(config-l2vpn-bg-bd)# interface TenGigE0/5/0/6/0.1
Router(config-l2vpn-bg-bd)# routed interface BVI1

Running Configuration

interface BVI1
 host-routing
 mtu 8986
 ipv4 address 10.1.1.1 255.255.255.0
 ipv6 address 10:1:1::1/120
!
interface TenGigE0/5/0/6/0.1 l2transport
 encapsulation dot1q 1
 rewrite ingress tag pop 1 symmetric
!
l2vpn
 bridge group 1
  bridge-domain 1
   interface TenGigE0/5/0/6/0.1
   !
   routed interface BVI1
   !

Repeat the configuration on the peer router.


/* Configure BGP as the routing protocol  */
Router(config)# router bgp 1
Router(config-bgp)# neighbor 2.2.1.1
Router(config-bgp-nbr)# remote-as 1
Router(config-bgp-nbr)# bfd fast-detect
Router(config-bgp-nbr)# bfd minimum-interval 300
Router(config-bgp-nbr)# update-source Loopback1
Router(config-bgp-nbr)# address-family ipv4 unicast

/* Configure reachability to the BGP neighbour IP either via static or IGP*/
Router(config-bgp-nbr-af)# router static
Router(config-static)# address-family ipv4 unicast
Router(config-static-afi)# 2.2.1.1/32 10.1.1.2 

/* Configure the line cards to allow hosting of Multipath BFD sessions. */
Router(config-static-afi)# bfd
Router(config-bfd)# 
 multipath include location 0/RP0/CPU0


router bgp 1 
neighbor 2.2.1.1
  remote-as 1
  bfd fast-detect
  bfd minimum-interval 300
  update-source Loopback1
  address-family ipv4 unicast
  !
router static
 address-family ipv4 unicast
  2.2.1.1/32 10.1.1.2
 !
bfd
 multipath include location 0/RP0/CPU0!

Note

To avoid the unsupported three-level recursion on BVI interfaces on the first and second generation of line cards, you must not configure the BVI interface as the next-hop in the static route configuration.

Verification

Router# show bfd session destination 2.2.1.1
Fri May 28 14:35:52.566 IST

Src Addr            Dest Addr       VRF Name                      H/W NPU          
                                        Local det time(int*mult)      State     
                                    Echo             Async           
------------------- --------------- ---------------- ---------------- ----------
1.1.1.1             2.2.1.1         default                       Yes 0/RP0/CPU0     
                                    n/a              900ms(300ms*3)   UP

Bias-Free Language

Results

Chapter: Implementing BFD

Implementing BFD

BFD Overview

Restrictions

BFD Timers

Enable and Disable IPv6 Checksum Calculations for BFD on a Router

Configure BFD Under a Dynamic Routing Protocol or Use a Static Route

Enable BFD for OSPF on an Interface

Running Configuration

Verification

Enable BFD over BGP

Running Configuration

Verification

Enable BFD on an IPv4 Static Route

Running Configuration

Verification

Enable BFD on an IPv6 Static Route

Running Configuration

Verification

Clear and Display BFD Counters

BFD over Bundle

BFD over Bundle

Configure BFD Over Bundle

BFD over Bundle

Restrictions for BFD over Bundle

Configure BFD over Bundle

Running Configuration

Verification

Configuration Example

Enabling BFD on a BGP Neighbor

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Enabling BFD for OSPF on an Interface

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Enabling BFD on a Static Route

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Enabling BFD Sessions on Bundle Members

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Specifying the BFD Destination Address on a Bundle

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Configuring the Minimum Thresholds for Maintaining an Active Bundle

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Configuring BFD Packet Transmission Intervals and Failure Detection Times on a Bundle

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