Implementing BFD

Bidirectional forwarding detection (BFD) provides low-overhead, short-duration detection of failures in the path between adjacent forwarding engines. 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.


Tip

You can programmatically configure BFD and retrieve operational data using openconfig-bfd.yang OpenConfig data model. To get started with using data models, see the Programmability Configuration Guide.

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 multihop is supported starting from IOS XR Release 6.3.2 but BFD multihop over non IP core is not supported.

  • 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.

  • Only IETF mode is supported in BFD over bundle feature.

  • 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.

SNMP traps are not supported for multipath BFD sessions.

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

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

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

  • It is only supported in IETF mode.

  • It is only supported on main bundle interface; it is not supported on bundle sub-interfaces.

  • It is not supported on routing protocols, such as OSPF, ISIS, and BGP.

  • When 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

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

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 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

debouncedebounce

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 1. 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 ++