Excluding prefixes from LFA SPF

In the current SR OS implementation, the user can exclude an interface in IS-IS or OSPF, an OSPF area, or an IS-IS level from the LFA SPF.

This feature adds the ability to exclude prefixes from a prefix policy which matches on prefixes or on IS-IS tags:

config>router>isis>loopfree-alternate-exclude prefix-policy prefix-policy1 [prefix-policy2…up to 5]

config>router>ospf>loopfree-alternate-exclude prefix-policy prefix-policy1 [prefix-policy2…up to 5]

Example

The prefix policy is configured as in the existing SR OS implementation.

config
        router
            policy-options
                [no] prefix-list prefix-list1
                    prefix 10.225.16.0/24 prefix-length-range 32-32
                [no] policy-statements prefix-policy1
                    entry 10
                    from
                        prefix-list "prefix-list1"
                     exit
                        action accept
                    exit
                exit
                default-action reject
    exit

The default action of the preceding loopfree-alternate-exclude command when not specified by the user in the prefix policy is a ‟reject”. Therefore, regardless of whether the user explicitly added the statement ‟default-action reject” to the prefix policy, a prefix which does not match any entry in the policy is accepted into LFA SPF.