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CLI-based Configuration Guide - IP Unicast Routing

AR100, AR120, AR150, AR160, AR200, AR1200, AR2200, AR3200, and AR3600 V200R009

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Enabling OSPF IP FRR

Enabling OSPF IP FRR

Context

Enabling OSPF IP FRR to generate a loop-free backup link. When this route becomes faulty, OSPF can fast switch the traffic to a backup link.

FRR calculation consumes a large number of CPU resources. When there are import features such as routing protocol, you need to delay FRR calculation.

After FRR calculation is delayed, devices process important services such as route calculation first.

Do as follows on the router that needs to protect traffic to be forwarded:

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run ospf [ process-id | router-id router-id | vpn-instance vpn-instance-name ] *

    An OSPF process is started and the OSPF view is displayed.

  3. Run frr

    The OSPF IP FRR view is displayed.

  4. Run loop-free-alternate

    OSPF IP FRR is enabled to generate a loop-free backup link.

    NOTE:

    OSPF can generate a loop-free backup link only when the OSPF IP FRR traffic protection inequality is met.

  5. (Optional) Run frr-priority static low

    The Loop-Free Alternates (LFA) algorithm is used to calculate the nexthop and outbound interface for a backup link.

    The nexthop and outbound interface of an OSPF loop-free backup link can be obtained using either of the following methods:

    • For a static backup link, after IP FRR is enabled using the ip frr command in the system view or ip frr command in VPN instance view, configure a nexthop and an outbound interface for the static backup link.
    • For a dynamic backup link, after OSPF IP FRR is enabled using the loop-free-alternate command, enable the device to use the LFA algorithm to calculate the nexthop and outbound interface for the dynamic backup link.

    By default, static backup links take preference over dynamic backup links during route selection. However, static backup links are less flexible than dynamic backup links. If a link failure occurs, static backup links cannot update automatically, but dynamic backup links can. Therefore, to ensure automatic link updates, run the frr-priority static low command to enable dynamic backup links to take preference over static backup links so that the LFA algorithm is used to calculate the nexthop and outbound interface.

  6. (Optional) Run frr-policy route route-policy route-policy-name

    OSPF IP FRR filtering policies are configured.

    After OSPF IP FRR filtering policies are configured, only the OSPF backup routes that match the filtering conditions can be delivered to the forwarding table. To protect the traffic over a specific OSPF route, you can configure a filtering policy that matches the OSPF route to ensure that the route can be added to the forwarding table. When this route becomes faulty, OSPF can fast switch the traffic to a backup link.

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Updated: 2019-05-17

Document ID: EDOC1000174069

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