Excluding prefixes from LFA SPF

In the current 7210 SAS 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-policy [prefix-policy.. up to 5]

config>router>ospf>loopfree-alternate-exclude prefix-policy prefix-policy [prefix-policy.. 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 explicitly 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 that did not match an entry in the policy is accepted into LFA SPF.