Loop-Free Alternate Fast Reroute

Loop-Free Alternate (LFA) Fast Reroute (FRR) is a mechanism that provides local protection for unicast traffic in order to rapidly converge traffic flows around link and/or node failures.

Prerequisites for Loop-Free Alternate Fast Reroute

  • Any of the following protocols must be supported for Loop-Free Alternate Fast Reroute:

    • Intermediate System-to-Intermediate System (IS-IS)

    • Open Shortest Path First (OSPF)

  • While configuring ISIS protocol, isis network point-to-point must be configured.

Restrictions for Loop-Free Alternate Fast Reroute

  • Logical interfaces namely Port-channel (PoCH) support LFA FRR and remote LFA-FRR, with a single member link. Port-channel can be used as a backup path.

  • Micro loops may form due to traffic congestion.

  • A Multiprotocol Label Switching (MPLS) traffic engineering (TE) tunnel cannot be used as a protected interface. However, an MPLS-TE tunnel can be a protecting (repair) interface as long as the TE tunnel is used as a primary path.


    Note

    VPLS over TE Tunnel or TE FRR is not supported on the Cisco ASR 900 RSP3 module.

  • For TDM psuedowires, the interfaces supported are CEM on OC-3.


    Note

    This restriction is applicable only on the Cisco RSP3 Modules (NCS 4206 and NCS 4216).

  • Each bridge domain interface (BDI) protected by FRR can have only one EFP.

  • Remote LFA FRR provides better convergence with SFP ports rather than copper ports. As a workaround for copper ports, BFD triggered FRR can be used.

  • FRR is not supported with POS and serial interfaces.

  • Scale limit for FRR-protected global prefixes is 1500 and for layer 3 VPNs, scale limit is 4000.

Information About Loop-Free Alternate Fast Reroute

The Loop-Free Alternate (LFA) Fast Reroute (FRR) feature offers an alternative to the MPLS Traffic Engineering Fast Reroute feature to minimize packet loss due to link or node failure.

LFA FRR enables a backup route to avoid traffic loss if a network fails. The backup routes (repair paths) are precomputed and installed in the router as the backup for the primary paths. After the router detects a link or adjacent node failure, it switches to the backup path to avoid traffic loss.

LFA is a node other than the primary neighbor. Traffic is redirected to an LFA after a network failure. An LFA makes the forwarding decision without any knowledge of the failure. An LFA must neither use a failed element nor use a protecting node to forward traffic. An LFA must not cause loops. By default, LFA is enabled on all supported interfaces as long as the interface can be used as a primary path.

Advantages of using per-prefix LFAs are as follows:

  • The repair path forwards traffic during transition when the primary path link is down.

  • All destinations having a per-prefix LFA are protected. This leaves only a subset (a node at the far side of the failure) unprotected.

Supported Information

  • LFA FRR is supported with equal cost multipath (ECMP).

  • Fast Reroute triggered by Bidirectional Forwarding (BFD) is supported.

  • Remote LFA tunnels are High Availability aware; hence, Stateful Switchover (SSO) compliant.

Benefits of Loop-Free Alternate Fast Reroute

  • Same level of protection from traffic loss

  • Simplified configuration

  • Link and node protection

  • Link and path protection

  • LFA (loop-free alternate) paths

  • Support for both IP and Label Distribution Protocol (LDP) core

  • LFA FRR is supported with equal cost multipath (ECMP).

  • Fast Reroute triggered by Bidirectional Forwarding (BFD).

  • Remote LFA tunnels are High Availability aware; hence, Stateful Switchover (SSO) compliant.

LFA FRR and Remote LFA FRR over Bridge Domains Interfaces

The router supports bridge domain interfaces (BDI).

LFA FRR and remote LFA FRR is supported on bridge domain interfaces on the router.

IS-IS and IP FRR

When a local link fails in a network, IS-IS recomputes new primary next-hop routes for all affected prefixes. These prefixes are updated in the RIB and the Forwarding Information Base (FIB). Until the primary prefixes are updated in the forwarding plane, traffic directed towards the affected prefixes are discarded. This process can take hundreds of milliseconds.

In IP FRR, IS-IS computes LFA next-hop routes for the forwarding plane to use in case of primary path failures. LFA is computed per prefix.

When there are multiple LFAs for a given primary path, IS-IS uses a tiebreaking rule to pick a single LFA for a primary path. In case of a primary path with multiple LFA paths, prefixes are distributed equally among LFA paths.

Repair Paths

Repair paths forward traffic during a routing transition. When a link or a router fails, due to the loss of a physical layer signal, initially, only the neighboring routers are aware of the failure. All other routers in the network are unaware of the nature and location of this failure until information about this failure is propagated through a routing protocol, which may take several hundred milliseconds. It is, therefore, necessary to arrange for packets affected by the network failure to be steered to their destinations.

A router adjacent to the failed link employs a set of repair paths for packets that would have used the failed link. These repair paths are used from the time the router detects the failure until the routing transition is complete. By the time the routing transition is complete, all routers in the network revise their forwarding data and the failed link is eliminated from the routing computation.

Repair paths are precomputed in anticipation of failures so that they can be activated the moment a failure is detected.

The IPv4 LFA FRR feature uses the following repair paths:

  • Equal Cost Multipath (ECMP) uses a link as a member of an equal cost path-split set for a destination. The other members of the set can provide an alternative path when the link fails.

  • LFA is a next-hop route that delivers a packet to its destination without looping back. Downstream paths are a subset of LFAs.

Remote LFA FRR

Some topologies (for example the commonly used ring-based topology) require protection that is not afforded by LFA FRR alone. Consider the topology shown in the figure below:

Figure 1. Remote LFA FRR with Ring Topology

The red looping arrow represents traffic that is looping immediately after a failure between node A and C (before network reconvergence). Device A tries to send traffic destined to F to next-hop B. Device B cannot be used as an LFA for prefixes advertised by nodes C and F. The actual LFA is node D. However, node D is not directly connected to the protecting node A. To protect prefixes advertised by C, node A must tunnel the packet around the failed link A-C to node D, provided that the tunnel does not traverse the failing link.

Remote LFA FRR enables you to tunnel a packet around a failed link to a remote loop-free alternate that is more than one hop away. In the figure above, the green arrow between A and D shows the tunnel that is automatically created by the remote LFA feature to bypass looping.

Remote LFA FRR for TDM and ATM Psuedowires

The Router supports two pseudowire types that utilize CEM transport: Structure-Agnostic TDM over Packet (SAToP) and Circuit Emulation Service over Packet-Switched Network (CESoPSN).

Border Gateway Protocol (BGP) Prefix-Independent Convergence (PIC) and LFA FRR Integration

Both the Labeled Border Gateway Protocol (BGP) Prefix-Independent Convergence (PIC) feature and the Loop-Free Alternate (LFA) Fast Reroute (FRR) feature can be configured together on the router.

BGP PIC is supported for bridge domain interfaces (BDI) with FRR.


Note
Each bridge domain interface (BDI) protected by FRR can have only one EFP.

For information on configuring BGP PIC, see BGP PIC Edge for IP and MPLS-VPN.

Remote LFA FRR with VPLS

VPLS (Virtual Private LAN Service) enables enterprises to link together their Ethernet-based LANs from multiple sites via the infrastructure provided by their service provider. For information on configuring VPLS, see Configuring Virtual Private LAN Services. Starting With Cisco IOS XE Release 3.10S, Remote LFA FRR is supported with VPLS.

For information on configuring remote LFA FRR with VPLS, see How to Configure Loop-Free Alternate Fast Reroute.

Remote LFA for MLDP

Table 1. Feature History Table

Feature Name

Release Information

Description

Remote LFA for MLDP

 Cisco IOS XE Bengaluru 17.6.1

Remote Loop-Free Alternate (RLFA) based Fast Reroute (FRR) improves LFA coverage. When used with Multicast Label Distribution Protocol (MLDP) for IPv4, there’s no need for an extra protocol in the control plane.

Loop-Free Alternate (LFA) FRR mechanism enables a backup route to avoid traffic loss if a network fails. The backup routes are precomputed and installed in the router as backup for primary paths. After the Cisco router detects a link or adjacent node failure, it switches to the backup path to avoid traffic loss. As the backup paths are pre-calculated and installed, switching to back up path is fast, in case of failure.

Effective Cisco IOS XE Bengaluru 17.6.1, you can enable this feature to effectively use backup routes to help with load balancing. This feature improves the LFA coverage when used with MPLS LDP (MLDP), there’s no need of an extra protocol in the control plane.

Restrictions for Remote LFA for MLDP

  • MLDP Node protection is not supported.

  • Only Link Level protection for MLDP LFA FRR is supported.

  • The detection of local/ remote link failure and switch over to the repair path is performed within 100 msec irrespective of the FRR scale.

  • RLFA FRR in MLDP for IPv6 is not supported.

  • RLFA FRR for Port-channel is not supported.

  • Maximum supported Data Multicast Distribution Trees (MDT) for RLFA FRR is 750.

  • Make Before Break (MBB) timer should be configured based on the scale of prefixes and P2MP trees configured.

  • Label Distribution Protocol (LDP), Graceful Restart (GR) and MBB are mandatory to manage new and old Label Switch Path (LSP).

  • Duplicate traffic is observed during cutover until GR timer expires. Duplicate traffic is dropped in the merge node and is not received by the receiver.

  • RLFA over ECMP paths for mLDP is not supported.

  • You must configure microloop avoidance under the IGP instance to achieve the desired convergence parameters.


Note

Microloop avoidance may not work when Interior Gateway Protocol (IGP) is not receiving the interface down event to trigger the microloop avoidance timer. In such cases to avoid traffic drop due to IGP convergence, you have to configure BFD over the RLFA enabled links with 3.3-msec link down timers. This enables BFD to send link down notification within 9.9 msecs.

How to Configure Loop-Free Alternate Fast Reroute

To enable loop-free alternate fast reroute support for L2VPNs, VPLS, TDM pseudowires and VPWS, you must configure LFA FRR for the routing protocol. You can enable LFA FRR using ISIS or OSFP configurations.

Configuring IS-IS Remote Loop-Free Alternate Fast Reroute

The following additional configurations are mandatory:

  • mpls ldp discovery targeted-hello accept

Procedure

  Command or Action Purpose

Step 1

enable

Example:


Device> enable
Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.

Step 3

router isis [area-tag]

Example:


Device(config)# router isis ipfrr

Enables the IS-IS routing protocol and specifies an IS-IS process.

  • Enters router configuration mode.

Step 4

fast-reroute per-prefix {level-1 | level-2} {all | route-map route-map-name}

Example:


Device (config-router)#  fast-reroute per-prefix level-1 all

Enables per-prefix FRR.

  • Configure the all keyword to protect all prefixes.

Step 5

fast-reroute remote-lfa {level-1 | level-2} mpls-ldp [maximum-metric metric-value]

Example:


Device(config-router)# fast-reroute remote-lfa level-1 mpls-ldp
Configures an FRR path that redirects traffic to a remote LFA tunnel for either level 1 or level 2 packets.

  • Use the maximum-metric metric-value keyword-argument pair to specify the maximum metric value required to reach the release node.

Step 6

end

Example:


Device(config-router)# end

Exits router configuration mode and enters privileged EXEC mode.

Recommended Configurations ISIS

For optimal results with remote LFA FRR, it is recommended that you use the following SFP timers:

  • ISIS

    • spf-interval 5 50 200

    • prc-interval 5 50 200

    • sp-gen-interval 5 50 200

    • fast-flood 10

  • Globally configure the MPLS IGP hold-down timer to avoid an indefinite wait by IGP for synchronization using the mpls ldp igp sync holdown 2000 command.

Example: Configuring IS-IS Remote Loop-Free Alternate Fast Reroute

The following example shows how to enable remote LFA FRR: 


Router(config)# router isis
Router(config)# fast-reroute per-prefix level-1 all
Router(config)# fast-reroute per-prefix level-2 all
Router(router-config)# fast-reroute remote-lfa level-1 mpls-ldp
Router(router-config)# fast-reroute remote-lfa level-2 mpls-ldp

Example: Configuring Remote LFA FRR with VPLS

Example: Configuration of Remote LFA FRR with Interior Gateway Protocol (IGP)

router isis hp
 net 49.0101.0000.0000.0802.00
 is-type level-2-only
 ispf level-2
 metric-style wide
 fast-flood
 set-overload-bit on-startup 180
 max-lsp-lifetime 65535
 lsp-refresh-interval 65000
 spf-interval 5 50 200
 prc-interval 5 50 200
 lsp-gen-interval 5 5 200
 no hello padding
 log-adjacency-changes
 nsf cisco
 fast-reroute per-prefix level-1 all
 fast-reroute per-prefix level-2 all
 fast-reroute remote-lfa level-1 mpls-ldp
 fast-reroute remote-lfa level-2 mpls-ldp
 passive-interface Loopback0
 mpls ldp sync
 mpls traffic-eng router-id Loopback0
 mpls traffic-eng level-2

Example: Configuration of Remote LFA FRR with VPLS at the interface level.

!
interface GigabitEthernet0/3/3
 ip address 198.51.100.1 255.255.255.0
 ip router isis hp
 logging event link-status
 load-interval 30
 negotiation auto
 mpls ip
 mpls traffic-eng tunnels
 isis network point-to-point 
end
!

Example: Configuration of remote LFA FRR with VPLS at the global level.

!
l2 vfi Test-2000 manual 
 vpn id 2010
 bridge-domain 2010
 neighbor 192.0.2.1 encapsulation mpls
!

Example: Configuration of remote LFA FRR with VPLS at Access side.

!
interface TenGigabitEthernet0/2/0
 no ip address
 service instance trunk 1 ethernet
  encapsulation dot1q 12-2012
  rewrite ingress tag pop 1 symmetric
  bridge-domain from-encapsulation
 !

How to Configure OSPF IPv4 Remote Loop-Free Alternate IP Fast Reroute

Configuring a Remote LFA Tunnel

Perform this task to configure a per-prefix LFA FRR path that redirects traffic to a remote LFA tunnel.

Procedure
  Command or Action Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

router ospf process-id

Example:

Device(config)# router ospf 10

Enables OSPF routing and enters router configuration mode.

Step 4

fast-reroute per-prefix remote-lfa [area area-id] tunnel mpls-ldp

Example:

Device(config-router)# fast-reroute per-prefix remote-lfa area 2 tunnel mpls-ldp

Configures a per-prefix LFA FRR path that redirects traffic to a remote LFA tunnel via MPLS-LDP.

  • Use the area area-id keyword and argument to specify an area in which to enable LFA FRR.

Configuring the Maximum Distance to a Tunnel Endpoint

Perform this task to configure the maximum distance to the tunnel endpoint in a per-prefix LFA FRR path that redirects traffic to a remote LFA tunnel.

Procedure
  Command or Action Purpose

Step 1

enable

Example:

Device> enable
Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

router ospf process-id

Example:

Device(config)# router ospf 10

Enables OSPF routing and enters router configuration mode.

Step 4

fast-reroute per-prefix remote-lfa [area area-id] maximum-cost distance

Example:

Device(config-router)# fast-reroute per-prefix remote-lfa area 2 maximum-cost 30
Configures the maximum distance to the tunnel endpoint in a per-prefix LFA FRR path that redirects traffic to a remote LFA tunnel.

  • Use the area area-id keyword and variable to specify an area in which to enable LFA FRR.

Configuring Remote LFA FRR for MLDP

Perform this task to configure the LDP based Remote LFA FRR for MLDP.


Note

Ensure to configure a carrier delay down of 1 second on all core interfaces.

You must configure the mpls mldp forwarding recursive command to enable recursive forwarding. Do not disable this command while configuring Remote LFA MLDP.

Procedure

  Command or Action Purpose

Step 1

enable

Example:

Router enable

Enables privileged EXEC mode. Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

mpls ldp graceful-restart

Example:

Router(config)# mpls ldp graceful-restart

Enables the router to protect the LDP bindings and MPLS forwarding state during a disruption in service.

Step 4

mpls traffic-eng tunnels

Example:

Router(config)# mpls traffic-eng tunnels

Enables MPLS traffic engineering tunnel signaling on a device.

Step 5

mpls ldp discovery targeted-hello accept

Example:

Router(config)#mpls ldp discovery targeted-hello accept

Enables MPLS LDP targeted discovery on a device.

Step 6

mpls mldp make-before-break delay 1000

Example:

Router(config)#mpls mldp make-before-break delay 1000

Enables MPLS MLDP MBB on a device.

Step 7

end

Example:

Router(config)# end

Exits router configuration mode and enters privileged EXEC mode.

Configuring IGP based Remote LFA for MLDP

Perform this task to configure the IGP based Remote LFA MLDP.

Procedure

  Command or Action Purpose

Step 1

enable

Example:

Router enable

Enables privileged EXEC mode. Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

router ospf process-id

Example:

Router(config-router)# router ospf 10

Enables OSPF routing and enters router configuration mode.

Step 4

microloop avoidance rib-update-delay delay-time

Example:

Router(config-router)# microloop avoidance rib-update-delay 60000

Specifies the amount of time the node uses the microloop avoidance policy before updating its forwarding table. The delay-time is in milliseconds. The range is from 1-60000.

Step 5

fast-reroute per-prefix enable prefix-priority priority-level

Example:

Router(config-router)# fast-reroute per-prefix enable prefix-priority low

Enables repair-path computation and selects the priority level for repair paths.

Low priority specifies that all prefixes have the same eligibility for protection. High priority specifies that only high-priority prefixes are protected.

Step 6

fast-reroute per-prefix remote-lfa [area area-id] tunnel mpls-ldp

Example:

Router(config-router)# fast-reroute per-prefix remote-lfa area 0 tunnel mpls-ldp

Configures a per-prefix LFA FRR path that redirects traffic to a remote LFA tunnel via MPLS-LDP.

Use the area area-id keyword and argument to specify an area in which to enable LFA FRR.

Step 7

fast-reroute keep-all-paths

Example:

Router(config-router)# fast-reroute keep-all-paths

Specifies creating a list of repair paths considered for LFA FRR.

Step 8

end

Example:

Router(config)# end

Exits router configuration mode and enters privileged EXEC mode.

Verifying Remote LFA for MLDP


Note

The prefix 3.3.3.3 is mLDP Next Hop (NH) in the direction of receiver. 

Router#show ip cef 3.3.3.3 internal        
3.3.3.3/32, epoch 2, RIB[I], refcnt 9, per-destination sharing
  sources: RIB, RR, LTE 
  feature space:
    IPRM: 0x00028000
    Broker: linked, distributed at 1st priority
    LFD: 3.3.3.3/32 1 local label
    dflt local label info: global/16 [0x3]
        contains path extension list
        dflt disposition chain 0x37D08728
          label implicit-null
          FRR Primary
            <primary: IP adj out of GigabitEthernet0/0/5, addr 10.1.1.2>
        dflt label switch chain 0x37D08488
          label implicit-null
          FRR Primary
            <primary: TAG adj out of GigabitEthernet0/0/5, addr 10.1.1.2>
  subblocks:
    3 RR sources [no flags]
      non-eos chain [implicit-null|17](ptr:0x37D08488)-(local:16)
  ifnums:
    GigabitEthernet0/0/5(12): 10.1.1.2
    MPLS-Remote-Lfa2(47)
  path list 3711ACA0, 3 locks, per-destination, flags 0x49 [shble, rif, hwcn]
    path 2A05F610, share 1/1, type attached nexthop, for IPv4, flags [has-rpr]
      MPLS short path extensions: [none] MOI flags = 0x21 label implicit-null
      nexthop 10.1.1.2 GigabitEthernet0/0/5 label [implicit-null|17](ptr:0x37D08728)-(local:16), IP adj out of GigabitEthernet0/0/5, addr 10.1.1.2 379E4940
        repair: attached-nexthop 5.5.5.5 MPLS-Remote-Lfa2 (2A05F2E0)
    path 2A05F2E0, share 1/1, type attached nexthop, for IPv4, flags [rpr, rpr-only]
      nexthop 5.5.5.5 MPLS-Remote-Lfa2, repair, IP midchain out of MPLS-Remote-Lfa2 379E5740
  output chain:
    label [implicit-null|17](ptr:0x37D08728)-(local:16)
    FRR Primary (0x36EE6520)
      <primary: IP adj out of GigabitEthernet0/0/5, addr 10.1.1.2 379E4940>
      <repair:  TAG midchain out of MPLS-Remote-Lfa2 379E7340
                label 25-(local:24)
                TAG adj out of GigabitEthernet0/1/7, addr 60.1.1.2 379E4F40>

The following is sample output from the show ip mfib vrf command: 

Router3#show ip mfib vrf vrf1 232.0.0.1
Entry Flags:    C - Directly Connected, S - Signal, IA - Inherit A flag,
                ET - Data Rate Exceeds Threshold, K - Keepalive
                DDE - Data Driven Event, HW - Hardware Installed
                ME - MoFRR ECMP entry, MNE - MoFRR Non-ECMP entry, MP - MFIB 
                MoFRR Primary, RP - MRIB MoFRR Primary, P - MoFRR Primary
                MS  - MoFRR  Entry in Sync, MC - MoFRR entry in MoFRR Client,
                e   - Encap helper tunnel flag.
I/O Item Flags: IC - Internal Copy, NP - Not platform switched,
                NS - Negate Signalling, SP - Signal Present,
                A - Accept, F - Forward, RA - MRIB Accept, RF - MRIB Forward,
                MA - MFIB Accept, A2 - Accept backup,
                RA2 - MRIB Accept backup, MA2 - MFIB Accept backup

Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kbits per second
Other counts:      Total/RPF failed/Other drops
I/O Item Counts:   HW Pkt Count/FS Pkt Count/PS Pkt Count   Egress Rate in pps
VRF vrf1
 (100.1.1.2,232.0.0.1) Flags: HW
   SW Forwarding: 0/0/0/0, Other: 0/0/0
   HW Forwarding:   6106/1/100/1, Other: 0/0/0
   GigabitEthernet0/1/0 Flags: A
   Lspvif2, LSM/6, RPF-ID: *, Flags: F
     Pkts: 0/0/0    Rate: 0 pps

The following is sample output from the show adjacency lspvif 2 internal command: 

Router#show adjacency Lspvif2 internal
Protocol Interface                 Address
IP       Lspvif2                   225.0.0.0(2) (incomplete)
                                   0 packets, 0 bytes
                                   epoch 0
                                   sourced in sev-epoch 80
                                   punt (rate-limited) packets
                                   no src set
                                   L3 mtu 1500
                                   Flags (0x882)
                                   Fixup disabled
                                   HWIDB/IDB pointers 0x3831A6DC/0x3929EAA0
                                   IP redirect disabled
                                   Switching vector: IPv4 incomplete adj oce
                                   IPv4 MFIB wire 0x3653E020
                                   LSM-ID: 0x0
                                   Platform adj-id: 0xF8000311, 0x0, tun_qos_dpidx:0

                                   Adjacency pointer 0x379E4740
                                   Next-hop 225.0.0.0
IP       Lspvif2                   225.0.0.0(4)
                                   connectionid 6
                                   0 packets, 0 bytes
                                   epoch 0
                                   sourced in sev-epoch 80
                                   empty encap string
                                   Multicast
                                   Next chain element:
                                     replicate
                                       0: label 28
                                          label [implicit-null|17](ptr:0x37D08488)-(local:16)
                                          FRR Primary (0x31EF4540)
                                            <primary: TAG adj out of GigabitEthernet0/0/5, addr 10.1.1.2 379E5140>
                                            <repair:  TAG midchain out of MPLS-Remote-Lfa2 379E7340
                                                      label 25-(local:24)
                                                      TAG adj out of GigabitEthernet0/1/7, addr 60.1.1.2 379E4F40>
                                     parent oce 0x37971348
                                   L3 mtu 1500
                                   Flags (0x8C6)
                                   Fixup disabled
                                   HWIDB/IDB pointers 0x3831A6DC/0x3929EAA0
                                   IP redirect disabled
                                   Switching vector: IPv4 midchain adj oce
                                   IPv4 MFIB wire 0x392A003C
                                   LSM-ID: 0x6
                                   MPLS subblock: flags 0x18 NSF PATH_SET
                                     Path Set Id 0x00000006   Num Paths 1   Owner MLDP   Flags 0xD   RefCount 3
                                       path recursive 3.3.3.3  label 28  MOI flags 0x1
                                       EOS output chain elements: replicate
                                         0: label 28
                                            label [implicit-null|17](ptr:0x37D08488)-(local:16)
                                            FRR Primary (0x31EF4540)
                                              <primary: TAG adj out of GigabitEthernet0/0/5, addr 10.1.1.2 379E5140>
                                              <repair:  TAG midchain out of MPLS-Remote-Lfa2 379E7340
                                                        label 25-(local:24)
                                                        TAG adj out of GigabitEthernet0/1/7, addr 60.1.1.2 379E4F40>
                                       NonEOS output chain elements: replicate
                                         0: label 28
                                            label [implicit-null|17](ptr:0x37D08488)-(local:16)
                                            FRR Primary (0x31EF4540)
                                              <primary: TAG adj out of GigabitEthernet0/0/5, addr 10.1.1.2 379E5140>
                                              <repair:  TAG midchain out of MPLS-Remote-Lfa2 379E7340
                                                        label 25-(local:24)
                                                        TAG adj out of GigabitEthernet0/1/7, addr 60.1.1.2 379E4F40>
                                       oce chain (0x37971348):
                                         replicate
                                           0: label 28
                                              label [implicit-null|17](ptr:0x37D08488)-(local:16)
                                              FRR Primary (0x31EF4540)
                                                <primary: TAG adj out of GigabitEthernet0/0/5, addr 10.1.1.2 379E5140>
                                                <repair:  TAG midchain out of MPLS-Remote-Lfa2 379E7340
                                                          label 25-(local:24)
                                                          TAG adj out of GigabitEthernet0/1/7, addr 60.1.1.2 379E4F40>
                                     adj-sb send-slotmask: 0x0
                                   Platform adj-id: 0x10EC, 0x0, tun_qos_dpidx:0

                                   Adjacency pointer 0x379E4540
                                   Next-hop 225.0.0.0
IP       Lspvif2                   227.0.0.0(3)
                                   connectionid 1
                                   0 packets, 0 bytes
                                   epoch 0
                                   sourced in sev-epoch 80
                                   empty encap string
                                   Inject p2mp Multicast
                                   L3 mtu 17940
                                     mtu update from interface suppressed
                                   Flags (0x8A6)
                                   Fixup disabled
                                   HWIDB/IDB pointers 0x3831A6DC/0x3929EAA0
                                   IP redirect disabled
                                   Switching vector: IPv4 no fixup adj oce
                                   LSM-ID: 0x1
                                   Platform adj-id: 0xF8000314, 0x0, tun_qos_dpidx:0

                                   Adjacency pointer 0x379E7540
                                   Next-hop 227.0.0.0
IPV6     Lspvif2                   FF0E::(2) (incomplete)
                                   0 packets, 0 bytes
                                   epoch 0
                                   sourced in sev-epoch 80
                                   punt (rate-limited) packets
                                   no src set
                                   L3 mtu 1500
                                   Flags (0x1882)
                                   Fixup disabled
                                   HWIDB/IDB pointers 0x3831A6DC/0x3929EAA0
                                   IP redirect enabled
                                   Switching vector: IPv6 adjacency oce
                                   IPv6 MFIB wire 0x3653E054
                                   LSM-ID: 0x0
                                   Platform adj-id: 0xF8000312, 0x0, tun_qos_dpidx:0

                                   Adjacency pointer 0x379E5940
                                   Next-hop FF0E::
IPV6     Lspvif2                   FF0E::(3)
                                   connectionid 5
                                   0 packets, 0 bytes
                                   epoch 0
                                   sourced in sev-epoch 80
                                   empty encap string
                                   Multicast
                                   Next chain element:
                                     label ipv6-explicit-null
                                     TAG midchain out of Lspvif2, addr FF0E::, cid: 5 379E5D40
                                     replicate
                                     parent oce 0x3791B5B0
                                   L3 mtu 1500
                                   Flags (0x18C6)
                                   Fixup disabled
                                   HWIDB/IDB pointers 0x3831A6DC/0x3929EAA0
                                   IP redirect enabled
                                   Switching vector: IPv6 midchain adjacency oce
                                   LSM-ID: 0x5
                                   MPLS subblock: flags 0x8 NSF
                                     Lspvif2 FF0E:: label ipv6-explicit-null
                                       oce chain (0x3791B5B0):
                                         label ipv6-explicit-null
                                         TAG midchain out of Lspvif2, addr FF0E::, cid: 5 379E5D40
                                         replicate
                                     adj-sb send-slotmask: 0x0
                                   Platform adj-id: 0x10DD, 0x0, tun_qos_dpidx:0

                                   Adjacency pointer 0x379E5F40
                                   Next-hop FF0E::
TAG      Lspvif2                   FF0E::(4)
                                   connectionid 5
                                   0 packets, 0 bytes
                                   epoch 0
                                   sourced in sev-epoch 80
                                   empty encap string
                                   Multicast
                                   Next chain element:
                                     replicate
                                     parent oce 0x37970E50
                                   L3 mtu 17940
                                   Flags (0x8C6)
                                   Fixup disabled
                                   HWIDB/IDB pointers 0x3831A6DC/0x3929EAA0
                                   IP redirect disabled
                                   Switching vector: MPLS midchain adjacency oce
                                   LSM-ID: 0x5
                                   MPLS subblock: flags 0x18 NSF PATH_SET
                                     Path Set Id 0x00000005   Num Paths 0   Owner MLDP   Flags 0xD   RefCount 3
                                       EOS output chain elements: replicate
                                       NonEOS output chain elements: replicate
                                       oce chain (0x37970E50):
                                         replicate
                                     adj-sb send-slotmask: 0x0
                                   Platform adj-id: 0x10DE, 0x0, tun_qos_dpidx:0

                                   Adjacency pointer 0x379E5D40
                                   Next-hop FF0E::
IPV6     Lspvif2                   FFFF::(3)
                                   connectionid 1
                                   0 packets, 0 bytes
                                   epoch 0
                                   sourced in sev-epoch 80
                                   empty encap string
                                   Inject p2mp Multicast
                                   L3 mtu 1500
                                   Flags (0x1886)
                                   Fixup disabled
                                   HWIDB/IDB pointers 0x3831A6DC/0x3929EAA0
                                   IP redirect enabled
                                   Switching vector: IPv6 adjacency oce
                                   LSM-ID: 0x1
                                   Platform adj-id: 0xF8000315, 0x0, tun_qos_dpidx:0

                                   Adjacency pointer 0x379E7940
                                   Next-hop FFFF::
TAG      Lspvif2                   FFFF::(3)
                                   connectionid 1
                                   0 packets, 0 bytes
                                   epoch 0
                                   sourced in sev-epoch 80
                                   empty encap string
                                   Inject p2mp Multicast
                                   L3 mtu 17940
                                   Flags (0x886)
                                   Fixup disabled
                                   HWIDB/IDB pointers 0x3831A6DC/0x3929EAA0
                                   IP redirect disabled
                                   Switching vector: MPLS adjacency oce
                                   LSM-ID: 0x1
                                   Platform adj-id: 0x10DA, 0x0, tun_qos_dpidx:0

                                   Adjacency pointer 0x379E5B40
                                   Next-hop FFFF::
Router#

Verifying Loop-Free Alternate Fast Reroute

Use one or more of the following commands to verify the LFA FRR configuration

  • show ip cef network-prefix internal

  • show mpls infrastructure lfd pseudowire internal

  • show platform hardware pp active feature cef database ipv4 network-prefix

Example: Verifying LFA FRR with L2VPN

show ip cef internal

The following is sample output from the show ip cef internal command: 

Device# show ip cef 16.16.16.16 internal 
16.16.16.16/32, epoch 2, RIB[I], refcount 7, per-destination sharing
  sources: RIB, RR, LTE 
  feature space:
   IPRM: 0x00028000
   Broker: linked, distributed at 1st priority
   LFD: 16.16.16.16/32 1 local label
   local label info: global/17
        contains path extension list
        disposition chain 0x3A3C1DF0
        label switch chain 0x3A3C1DF0
  subblocks:
   1 RR source [no flags]
    non-eos chain [16|44]
  ifnums:
   GigabitEthernet0/0/2(9): 7.7.7.2
   GigabitEthernet0/0/7(14): 7.7.17.9
  path 35D61070, path list 3A388FA8, share 1/1, type attached nexthop, for IPv4, flags has-repair
    MPLS short path extensions: MOI flags = 0x20 label 16
  nexthop 7.7.7.2 GigabitEthernet0/0/2 label [16|44], adjacency IP adj out of GigabitEthernet0/0/2, addr 7.7.7.2 35E88520
    repair: attached-nexthop 7.7.17.9 GigabitEthernet0/0/7 (35D610E0)
  path 35D610E0, path list 3A388FA8, share 1/1, type attached nexthop, for IPv4, flags repair, repair-only
  nexthop 7.7.17.9 GigabitEthernet0/0/7, repair, adjacency IP adj out of GigabitEthernet0/0/7, addr 7.7.17.9 3A48A4E0
  output chain: label [16|44]
  FRR Primary (0x35D10F60)
  <primary:  TAG adj out of GigabitEthernet0/0/2, addr 7.7.7.2 35E88380>
  <repair:  TAG adj out of GigabitEthernet0/0/7, addr 7.7.17.9 3A48A340>
Rudy17#show mpls infrastructure lfd pseudowire internal
PW ID: 1VC ID: 4, Nexthop address: 16.16.16.16
SSM Class: SSS HW
Segment Count: 1
VCCV Types Supported:  cw ra ttl
Imposition details:
 Label stack {22 16}, Output interface: Gi0/0/2
 Preferred path: not configured
 Control Word: enabled, Sequencing: disabled
 FIB Non IP entry: 0x35D6CEEC
 Output chain:  AToM Imp (locks 4) label 22 label [16|44]
  FRR Primary (0x35D10F60)
  <primary:  TAG adj out of GigabitEthernet0/0/2, addr 7.7.7.2 35E88380>
Disposition details:
 Local label: 16
 Control Word: enabled, Sequencing: disabled
 SSS Switch: 3976200193
 Output chain:  mpls_eos( connid router-alert AToM Disp (locks 5)/ drop)

show mpls infrastructure lfd pseudowire internal

The following is sample output from the show mpls infrastructure lfd pseudowire internal command: 

Device# show mpls infrastructure lfd pseudowire internal
PW ID: 1VC ID: 4, Nexthop address: 16.16.16.16
SSM Class: SSS HW
Segment Count: 1
VCCV Types Supported:  cw ra ttl
Imposition details:
 Label stack {22 16}, Output interface: Gi0/0/2
 Preferred path: not configured
 Control Word: enabled, Sequencing: disabled
 FIB Non IP entry: 0x35D6CEEC
 Output chain:  AToM Imp (locks 4) label 22 label [16|44]
  FRR Primary (0x35D10F60)
  <primary:  TAG adj out of GigabitEthernet0/0/2, addr 7.7.7.2 35E88380>
Disposition details:
 Local label: 16
 Control Word: enabled, Sequencing: disabled
 SSS Switch: 3976200193
 Output chain:  mpls_eos( connid router-alert AToM Disp (locks 5)/ drop)

show platform hardware pp active feature cef database

The following is sample output from the show platform hardware pp active feature cef database command: 

Device# show platform hardware pp active feature cef database ipv4 16.16.16.16/32
=== CEF Prefix ===
16.16.16.16/32 -- next hop: UEA Label OCE (PI:0x104abee0, PD:0x10e6b9c8)
                Route Flags: (0) 
                Handles (PI:0x104ab6e0) (PD:0x10e68140)
 
  HW Info:
    TCAM handle: 0x0000023f    TCAM index: 0x0000000d
    FID index  : 0x0000f804    EAID      : 0x0000808a
    MET        : 0x0000400c    FID Count : 0x00000000

=== Label OCE ===
  Label flags: 4
  Num Labels: 1
  Num Bk Labels: 1
  Out Labels: 16
  Out Backup Labels: 44
  Next OCE Type: Fast ReRoute OCE; Next OCE handle: 0x10e6f428

=== FRR OCE ===
  FRR type         : IP FRR
  FRR state        : Primary
  Primary IF's gid : 3
  Primary FID      : 0x0000f801
  FIFC entries     : 32
  PPO handle       : 0x00000000
  Next OCE         : Adjacency (0x10e63b38)
  Bkup OCE         : Adjacency (0x10e6e590)

=== Adjacency OCE ===
  Adj State: COMPLETE(0)   Address: 7.7.7.2 
  Interface: GigabitEthernet0/0/2   Protocol: TAG 
  mtu:1500, flags:0x0, fixups:0x0, encap_len:14 
  Handles (adj_id:0x00000039) (PI:0x1041d410) (PD:0x10e63b38) 
  Rewrite Str: d0:c2:82:17:8a:82:d0:c2:82:17:f2:02:88:47
 
  HW Info:
    FID index: 0x0000f486    EL3 index: 0x00001003    EL2 index: 0x00000000
    El2RW    : 0x00000107    MET index: 0x0000400c    EAID     : 0x00008060
    HW ADJ FLAGS: 0x40
    Hardware MAC Rewrite Str: d0:c2:82:17:8a:82:08:00:40:00:0d:02

=== Adjacency OCE ===
  Adj State: COMPLETE(0)   Address: 7.7.17.9 
  Interface: GigabitEthernet0/0/7   Protocol: TAG 
  mtu:1500, flags:0x0, fixups:0x0, encap_len:14 
  Handles (adj_id:0x00000012) (PI:0x104acbd0) (PD:0x10e6e590) 
  Rewrite Str: d0:c2:82:17:c9:83:d0:c2:82:17:f2:07:88:47
 
  HW Info:
    FID index: 0x0000f49d    EL3 index: 0x00001008    EL2 index: 0x00000000
    El2RW    : 0x00000111    MET index: 0x00004017    EAID     : 0x0000807d
    HW ADJ FLAGS: 0x40
    Hardware MAC Rewrite Str: d0:c2:82:17:c9:83:08:00:40:00:0d:07

Configuration Examples for OSPF IPv4 Remote Loop-Free Alternate IP Fast Reroute

Example: Configuring a Remote LFA Tunnel

The following example shows how to configure a remote per-prefix LFA FRR in area 2. The remote tunnel type is specified as MPLS-LDP: 


Router(config-router)# fast-reroute per-prefix remote-lfa area 2 tunnel mpls-ldp

Example: Configuring the Maximum Distance to a Tunnel Endpoint

The following example shows how to set a maximum cost of 30 in area 2: 


Router(config-router)# fast-reroute per-prefix remote-lfa area 2 maximum-cost 30

Example: Verifying Tunnel Interfaces Created by OSPF IPv4 Remote LFA IPFRR

The following example displays information about about tunnel interfaces created by OSPF IPv4 LFA IPFRR: 
Router# show ip ospf fast-reroute remote-lfa tunnels

						OSPF Router with ID (192.168.1.1) (Process ID 1)
						Area with ID (0)
						Base Topology (MTID 0)

Interface MPLS-Remote-Lfa3
	Tunnel type: MPLS-LDP
	Tailend router ID: 192.168.3.3
	Termination IP address: 192.168.3.3
	Outgoing interface: Ethernet0/0
	First hop gateway: 192.168.14.4
	Tunnel metric: 20
	Protects:
		192.168.12.2 Ethernet0/1, total metric 30

Verifying Remote Loop-Free Alternate Fast Reroute with VPLS

Example: Verifying Remote LFA FRR with VPLS

show ip cef internal

The following is sample output from the show ip cef internal command: 

Router# show ip cef 198.51.100.2/32 internal

198.51.100.2/32, epoch 2, RIB[I], refcount 7, per-destination sharing
  sources: RIB, RR, LTE 
  feature space:
   IPRM: 0x00028000
   Broker: linked, distributed at 1st priority
   LFD: 198.51.100.2/32 1 local label
   local label info: global/2033
        contains path extension list
        disposition chain 0x46764E68
        label switch chain 0x46764E68
  subblocks:
   1 RR source [heavily shared]
    non-eos chain [explicit-null|70]
  ifnums:
   TenGigabitEthernet0/1/0(15): 192.0.2.10
   MPLS-Remote-Lfa2(46)
  path 44CE1290, path list 433CF8C0, share 1/1, type attached nexthop, for IPv4, flags has-repair
    MPLS short path extensions: MOI flags = 0x21 label explicit-null
  nexthop 192.0.2.10 TenGigabitEthernet0/1/0 label [explicit-null|70], adjacency IP adj out of TenGigabitEthernet0/1/0, addr 192.0.2.10 404B3960
    repair: attached-nexthop 192.0.2.1 MPLS-Remote-Lfa2 (44CE1300)
  path 44CE1300, path list 433CF8C0, share 1/1, type attached nexthop, for IPv4, flags repair, repair-only
  nexthop 192.0.2.1 MPLS-Remote-Lfa2, repair, adjacency IP midchain out of MPLS-Remote-Lfa2 404B3B00
  output chain: label [explicit-null|70]
  FRR Primary (0x3E25CA00)
  <primary:  TAG adj out of TenGigabitEthernet0/1/0, addr 192.168.101.22 404B3CA0>
  <repair:  TAG midchain out of MPLS-Remote-Lfa2 404B37C0 label 37 TAG adj out of GigabitEthernet0/3/3, addr 192.0.2.14 461B2F20>

show ip cef detail

The following is sample output from the show ip cef detail command: 

Router# show ip cef 198.51.100.2/32 detail

198.51.100.2/32, epoch 2
  local label info: global/2033
  1 RR source [heavily shared]
  nexthop 192.0.2.14 TenGigabitEthernet0/1/0 label [explicit-null|70]
    repair: attached-nexthop 192.0.2.1 MPLS-Remote-Lfa2
  nexthop 192.0.2.1 MPLS-Remote-Lfa2, repair
!

show platform hardware pp active feature cef databas

The following is sample output from the show platform hardware pp active feature cef database command: 

Router# show platform hardware pp active feature cef database ipv4 198.51.100.2/32

=== CEF Prefix ===
198.51.100.2/32 -- next hop: UEA Label OCE (PI:0x10936770, PD:0x12dd1cd8)
                Route Flags: (0) 
                Handles (PI:0x109099c8) (PD:0x12945968)
 
  HW Info:
    TCAM handle: 0x00000266    TCAM index: 0x00000015
    FID index  : 0x00008e7f    EAID      : 0x0001d7c4
    MET        : 0x0000401c    FID Count : 0x00000000
=== Label OCE ===
  Label flags: 4
  Num Labels: 1
  Num Bk Labels: 1
  Out Labels: 0
  Out Backup Labels: 70
=== FRR OCE ===
  FRR type         : IP FRR
  FRR state        : Primary
  Primary IF's gid : 52
  Primary FID      : 0x00008cb6
  FIFC entries     : 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
  PPO handle       : 0x00000000
  Next OCE         : Adjacency (0x130e0df0)
  Bkup OCE         : Adjacency (0x130de608)

=== Adjacency OCE ===
  Adj State: COMPLETE(0)   Address: 192.168.101.22 
  Interface: TenGigabitEthernet0/1/0   Protocol: TAG 
  mtu:1500, flags:0x0, fixups:0x0, encap_len:14 
  Handles (adj_id:0x000016ac) (PI:0x1090cc10) (PD:0x130e0df0) 
  Rewrite Str: 18:33:9d:3d:83:10:c8:f9:f9:8d:04:10:88:47
HW Info:
    FID index: 0x00008e7e    EL3 index: 0x00001034    EL2 index: 0x00000000
    El2RW    : 0x0000010d    MET index: 0x00004012    EAID     : 0x0001d7c1
    HW ADJ FLAGS: 0x40
    Hardware MAC Rewrite Str: 18:33:9d:3d:83:10:08:00:40:00:0d:10
=== Adjacency OCE ===
  Adj State: COMPLETE(0)   Address: 0 
  Interface: MPLS-Remote-Lfa2   Protocol: TAG 
  mtu:17940, flags:0x40, fixups:0x0, encap_len:0 
  Handles (adj_id:0xf80002e8) (PI:0x10da2150) (PD:0x130de608) 
  Rewrite Str: 
 
  HW Info:
    FID index: 0x00008ca8    EL3 index: 0x0000101c    EL2 index: 0x00000000
    El2RW    : 0x00000003    MET index: 0x00004024    EAID     : 0x0001d7cb
    HW ADJ FLAGS: 0x40
    Hardware MAC Rewrite Str: 00:00:00:00:00:00:00:00:00:00:00:00

=== Label OCE ===
  Label flags: 4
  Num Labels: 1
Num Bk Labels: 1
  Out Labels: 37
  Out Backup Labels: 37
  Next OCE Type: Adjacency; Next OCE handle: 0x12943a00
=== Adjacency OCE ===
  Adj State: COMPLETE(0)   Address: 30.1.1.1 
  Interface: GigabitEthernet0/3/3   Protocol: TAG 
  mtu:1500, flags:0x0, fixups:0x0, encap_len:14 
  Handles (adj_id:0x0000378e) (PI:0x10909738) (PD:0x12943a00) 
  Rewrite Str: c8:f9:f9:8d:01:b3:c8:f9:f9:8d:04:33:88:47
 
  HW Info:
    FID index: 0x00008c78    EL3 index: 0x0000101c    EL2 index: 0x00000000
    El2RW    : 0x00000109    MET index: 0x0000400e    EAID     : 0x0001cf4b
    HW ADJ FLAGS: 0x40
    Hardware MAC Rewrite Str: c8:f9:f9:8d:01:b3:08:00:40:00:0d:33

show mpls l2transport detail

The following is sample output from the show mpls l2transport detail command: 

Router# show mpls l2transport vc 2000 detail

Local interface: VFI Test-1990 vfi up
  Interworking type is Ethernet
  Destination address: 192.0.2.1, VC ID: 2000, VC status: up
    Output interface: Te0/1/0, imposed label stack {0 2217}
    Preferred path: not configured  
    Default path: active
    Next hop: 192.51.100.22
  Create time: 1d08h, last status change time: 1d08h
    Last label FSM state change time: 1d08h
  Signaling protocol: LDP, peer 192.0.51.1:0 up
    Targeted Hello: 192.51.100.2(LDP Id) -> 192.51.100.200, LDP is UP
    Graceful restart: configured and enabled
    Non stop routing: not configured and not enabled
    Status TLV support (local/remote)   : enabled/supported
      LDP route watch                   : enabled
      Label/status state machine        : established, LruRru
      Last local dataplane   status rcvd: No fault
      Last BFD dataplane     status rcvd: Not sent
      Last BFD peer monitor  status rcvd: No fault
      Last local AC  circuit status rcvd: No fault
      Last local AC  circuit status sent: No fault
      Last local PW i/f circ status rcvd: No fault
      Last local LDP TLV     status sent: No fault
      Last remote LDP TLV    status rcvd: No fault

Verifying Tunnel Interfaces Created by OSPF IPv4 Remote LFA IPFRR

Procedure

  Command or Action Purpose

Step 1

enable

Example:


Device> enable
Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

show ip ospf fast-reroute remote-lfa tunnels

Example:

Device# show ip ospf fast-reroute remote-lfa tunnels

Displays information about the OSPF per-prefix LFA FRR configuration.

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Command List, All Releases

MPLS commands

Multiprotocol Label Switching Command Reference

Technical Assistance

Description

Link

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http://www.cisco.com/cisco/web/support/index.html