Configuring IPv6 IS-IS Auto FRR

With IPv6 IS-IS Auto FRR, traffic on a faulty link can be quickly switched to an alternate link, which minimizes traffic interruption and improves IS-IS network reliability.

Usage Scenario

As networks develop, Voice over Internet Protocol (VoIP) and online video services pose increasingly higher requirements for real-time transmission. Nevertheless, if an IS-IS fault occurs, multiple operations, including fault detection, LSP updating, LSP flooding, route calculation, and forward information base (FIB) entry delivery, must be performed to switch traffic to a new link. These operations take a long time, much longer than 50 ms, the minimum delay to which users are sensitive. As a result, user experience is affected.

With IPv6 IS-IS Auto FRR, devices can rapidly switch traffic from a faulty link to an alternate one without interrupting the traffic, which significantly improves IS-IS network reliability.

IPv6 IS-IS Auto FRR is applicable to the services that are sensitive to packet delay and packet loss.

IPv6 IS-IS Auto FRR can only take effect in the standard topology.

Pre-configuration Tasks

Before configuring IPv6 IS-IS Auto FRR, complete the following tasks:

Configure the link layer protocol on interfaces.
Configure IP addresses for interfaces and ensure that neighboring devices are reachable at the network layer.
Configure basic IPv6 IS-IS functions.
Configure a local LDP session on the source node, the PQ node, and the nodes between them if remote LFA FRR is required.

Procedure

Configure the LFA algorithm.
1. Run system-view
  The system view is displayed.
2. Run isis [ process-id ]
  The IS-IS process is enabled, and the IS-IS view is displayed.
3. Run ipv6 frr
  The IS-IS IPv6 FRR view is displayed.
4. (Optional) Run ecmp disable { level-1 | level-2 }
  The IPv6 IS-IS ECMP FRR is disabled.
  
  With ECMP FRR, IS-IS pre-calculates backup paths for load balancing links based on the LSDBs on the entire network. The backup paths are stored in the forwarding table and are used for traffic protection in the case of link failures. If the network topology changes, ECMP FRR triggers calculation of new backup paths, which increases the system calculation pressure. In addition, the backup entries generated by the ECMP FRR function increase the memory usage of the system. In this case, you can run the ecmp disable command to disable the ECMP FRR function.
5. Run loop-free-alternate [ level-1 | level-2 | level-1-2 ]
  LFA is enabled for IPv6 IS-IS Auto FRR.
  
  If no IS-IS level is specified, LFA is enabled for both Level-1 and Level-2 IPv6 IS-IS Auto FRR.
6. (Optional) Run frr-policy route route-policy route-policy-name
  A route-policy is configured to filter IS-IS alternate routes.
7. (Optional) Run tiebreaker { node-protecting | lowest-cost | non-ecmp | srlg-disjoint | hold-max-cost } preference preference [ level-1 | level-2 | level-1-2 ]
  The solution of selecting a backup path for IPv6 IS-IS Auto FRR is set.
8. Run commit
  The configuration is committed.
Configure the remote LFA algorithm.
1. Run system-view
  The system view is displayed.
2. Run isis [ process-id ]
  The IS-IS process is enabled, and the IS-IS view is displayed.
3. Run frr
  The IS-IS FRR view is displayed.
4. Run remote-lfa tunnel ldp [ maximum-reachable-cost cost-value ] [ level-1 | level-2 | level-1-2 ]
  Remote LFA Auto FRR is enabled.
5. Run quit
  The previous view is displayed.
6. Run ipv6 frr
  The IS-IS IPv6 FRR view is displayed.
7. (Optional) Run ecmp disable { level-1 | level-2 }
  The IS-IS IPv6 FRR view is displayed.
  
  With ECMP FRR, IS-IS pre-calculates backup paths for load balancing links based on the LSDBs on the entire network. The backup paths are stored in the forwarding table and are used for traffic protection in the case of link failures. If the network topology changes, ECMP FRR triggers calculation of new backup paths, which increases the system calculation pressure. In addition, the backup entries generated by the ECMP FRR function increase the memory usage of the system. In this case, you can run the ecmp disable command to disable the ECMP FRR function.
8. (Optional) Run remote-lfa tunnel ldp over-ipv4 [ level-1 | level-2 | level-1-2 ]
  Remote LFA Auto FRR is enabled.
  
  LFA FRR cannot calculate backup paths on some large IPv6 networks, especially on ring networks, which fails to meet reliability requirements. IPv6 IS-IS remote LFA FRR can address this problem. To enable IPv6 IS-IS remote LFA, run the remote-lfa command. The remote LFA algorithm calculates the PQ node based on the protection path and establishes a tunnel between the source node and the PQ node for backup next hop protection. If a fault occurs on the protection path, traffic is automatically switched to the backup tunnel, improving network reliability.
9. (Optional) Run tiebreaker { node-protecting | lowest-cost | non-ecmp | srlg-disjoint } preference preference [ level-1 | level-2 | level-1-2 ]
  The solution of selecting a backup path for IPv6 IS-IS Auto FRR is set.
10. Run commit
  The configuration is committed.

Checking the Configurations

After configuring IPv6 IS-IS Auto FRR, check the configurations.

Run the display isis route [ level-1 | level-2 ] [ process-id | vpn-instance vpn-instance-name ] ipv6 [ ipv6-address [ prefix-length ] ] [ verbose ] command to check information about the primary and alternate links after IPv6 IS-IS Auto FRR is enabled.
Run the display isis [ process-id ] srlg { srlgGroupId | all } command to check shared risk link group information.