Example: Configuring IPv6 IS-IS FRR

Network configuration

As shown in Figure 54, Switch A, Switch B, and Switch C belong to the same IS-IS routing domain. Configure IPv6 IS-IS FRR so that when the Link A fails, traffic can be switched to Link B immediately.

Figure 54: Network diagram

Table 17: Interface and IP address assignment

Device	Interface	IPv6 address	Device	Interface	IPv6 address
Switch A	Vlan-int100	1::1/64	Switch B	Vlan-int101	3::1/64
	Vlan-int200	2::1/64		Vlan-int200	2::2/64
	Loop0	10::1/128		Loop0	20::1/128
Switch C	Vlan-int100	1::2/64
	Vlan-int101	3::2/64

Procedure

IMPORTANT:

By default, interfaces on the device are disabled (in ADM or Administratively Down state). To have an interface operate, you must use the undo shutdown command to enable that interface.

Configure IPv6 addresses for interfaces on the switches and enable IPv6 IS-IS. (Details not shown.)
Configure IPv6 IS-IS on the switches to make sure Switch A, Switch B, and Switch C can communicate with each other at Layer 3. (Details not shown.)

Configure IPv6 IS-IS FRR:

Enable IPv6 IS-IS FRR to calculate a backup next hop through LFA calculation, or designate a backup next hop by using a routing policy.

(Method 1.) Enable IPv6 IS-IS FRR to calculate a backup next hop through LFA calculation:

# Configure Switch A.

<SwitchA> system-view
[SwitchA] isis 1
[SwitchA-isis-1] address-family ipv6
[SwitchA-isis-1-ipv6] fast-reroute lfa

# Configure Switch B.

<SwitchB> system-view
[SwitchB] isis 1
[SwitchB-isis-1] address-family ipv6
[SwitchB-isis-1-ipv6] fast-reroute lfa

(Method 2.) Enable IPv6 IS-IS FRR to designate a backup next hop by using a routing policy:

# Configure Switch A.

<SwitchA> system-view
[SwitchA] ipv6 prefix-list abc index 10 permit 20::1 128
[SwitchA] route-policy frr permit node 10
[SwitchA-route-policy-frr-10] if-match ipv6 address prefix-list abc
[SwitchA-route-policy-frr-10] apply ipv6 fast-reroute backup-interface vlan-interface 100 backup-nexthop 1::2
[SwitchA-route-policy-frr-10] quit
[SwitchA] isis 1
[SwitchA-isis-1] address-family ipv6
[SwitchA-isis-1-ipv6] fast-reroute route-policy frr
[SwitchA-isis-1-ipv6] quit
[SwitchA-isis-1] quit

# Configure Switch B.

<SwitchB> system-view
[SwitchB] ipv6 prefix-list abc index 10 permit 10::1 128
[SwitchB] route-policy frr permit node 10
[SwitchB-route-policy-frr-10] if-match ipv6 address prefix-list abc
[SwitchB-route-policy-frr-10] apply ipv6 fast-reroute backup-interface vlan-interface 101 backup-nexthop 3::2
[SwitchB-route-policy-frr-10] quit
[SwitchB] isis 1
[SwitchB-isis-1] address-family ipv6
[SwitchB-isis-1-ipv6] fast-reroute route-policy frr
[SwitchB-isis-1-ipv6] quit
[SwitchB-isis-1] quit

Verifying the configuration

# Display route 20::1/128 on Switch A to view the backup next hop information.

[SwitchA] display ipv6 routing-table 20::1 128 verbose 

Summary count : 1

Destination: 20::1/128
   Protocol: IS_L1
 Process ID: 1
  SubProtID: 0x1                    Age: 00h27m45s
       Cost: 10              Preference: 15
      IpPre: N/A             QosLocalID: N/A
        Tag: 0                    State: Active Adv
  OrigTblID: 0xa                OrigVrf: default-vrf
    TableID: 0xa                 OrigAs: 0
      NibID: 0x24000005          LastAs: 0
     AttrID: 0xffffffff        Neighbor: ::
      Flags: 0x10041        OrigNextHop: FE80::34CD:9FF:FE2F:D02
      Label: NULL           RealNextHop: FE80::34CD:9FF:FE2F:D02
    BkLabel: NULL             BkNextHop: FE80::7685:45FF:FEAD:102
  Tunnel ID: Invalid          Interface: Vlan-interface200
BkTunnel ID: Invalid        BkInterface: Vlan-interface100
   FtnIndex: 0x0           TrafficIndex: N/A
  Connector: N/A

# Display route 10::1/128 on Switch B to view the backup next hop information.

[SwitchB] display ipv6 routing-table 10::1 128 verbose

Summary count : 1

Destination: 10::1/128
   Protocol: IS_L1
 Process ID: 1
  SubProtID: 0x1                    Age: 00h33m23s
       Cost: 10              Preference: 15
      IpPre: N/A             QosLocalID: N/A
        Tag: 0                    State: Active Adv
  OrigTblID: 0xa                OrigVrf: default-vrf
    TableID: 0xa                 OrigAs: 0
      NibID: 0x24000006          LastAs: 0
     AttrID: 0xffffffff        Neighbor: ::
      Flags: 0x10041        OrigNextHop: FE80::34CC:E8FF:FE5B:C02
      Label: NULL           RealNextHop: FE80::34CC:E8FF:FE5B:C02
    BkLabel: NULL             BkNextHop: FE80::7685:45FF:FEAD:102
  Tunnel ID: Invalid          Interface: Vlan-interface200
BkTunnel ID: Invalid        BkInterface: Vlan-interface101
   FtnIndex: 0x0           TrafficIndex: N/A
  Connector: N/A

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