Configure IPv6 IS-IS Accept Policies

About this task

Perform the following procedure to create and enable IPv6 IS-IS accept policies based on a particular Backbone Edge Bridge (BEB), I-SID, or I-SID list. IPv6 IS-IS accept policies filter incoming IS-IS routes that the device receives over the SPBM cloud. IPv6 IS-IS accept policies apply to incoming traffic and determine whether to add the route to the routing table.

IPv6 IS-IS accept policies are disabled by default.

Note

• The I-SID lists created can be associated with both IPv4 or IPv6 routes.

• The ipv6 isis apply accept [vrf WORD<1-16>] command can disrupt traffic and cause temporary traffic loss. After you apply ipv6 isis apply accept [vrf <1-16>], the command reapplies the accept policies, which deletes all of the IS-IS routes, and adds the IS-IS routes again. You should make all the relevant accept policy changes, and then apply ipv6 isis apply accept [vrf WORD<1-16>] at the end.

• If the route policy associated with an accept policy changes, you must reapply the IPv6 IS-IS accept policy, unless the IPv6 IS-IS accept policy was the last sequence in the configuration.

• The ipv6 isis apply accept [vrf WORD<1-16>] command is not saved in the configuration file. If you use a saved configuration file for IPv6 IS-IS accept policy configuration, you must apply the ipv6 isis apply accept [vrf WORD<1-16>] command at the end.

  The number of unique Layer 3 VSN I-SIDs used on a BEB is limited to the number of VRFs supported on the switch. This includes the I-SID values used for Layer 3 VSNs and the I-SID values specified for the IPv6 IS-IS accept policy filters.

  The switch supports 24 VRFs by default, so, in a default configuration, you cannot create an I-SID list or accept policy with more than 24 unique I-SID entries. However, the configured VRFs take up an entry, so the formula to calculate the limit is: [24 VRF Limit – (currently configured VRFs)]. This gives the number of unique I-SIDs that can be used directly in the IPv6 IS-IS accept policy filters, which you implement with the ip isid-list or ipv6 accept command. The I-SIDs used for Layer 3 VSNs can be reused in IPv6 IS-IS accept policy filters without affecting the limit.

  If you increase the VRF scaling, you can create more Layer 3 VSNs. For more information about how to increase the number of supported VRFs, see Configure the Maximum Number of VRFs. The maximum number of supported VRFs and Layer 3 VSNs differs depending on the hardware platform. For more information about maximum scaling numbers, see Fabric Engine Release Notes.

1. Enter Global Configuration mode:

   enable

   configure terminal

2. Optional: If you want to accept routes from a variety of I-SIDs, create an I-SID list before you create an IPv6 IS-IS accept policy for the I-SID list:

   ip isid-list WORD<1–32> {<1–16777215> | list WORD<1–1024>}

   

   Note

   When creating an I-SID list, you can add I-SID entries until the maximum limit for supported Layer 3 I-SIDs is reached. The system truncates any additional I-SID entries. The maximum limit includes the I-SIDs for locally configured Layer 3 VSNs and the I-SIDs specified for IS-IS accept policy filters.

   Use the command show ip isid-list vrf WORD<1-16> to view the list of truncated I-SIDs.

3. Enter VRF Router Configuration mode for a specific VRF context:

   enable

   configure terminal

   router vrf WORD<1-16>

4. Configure an IPv6 IS-IS accept policy instance with a route policy.

   Use one of the following options:

   1. Configure an IPv6 IS-IS accept policy based on a specific advertising BEB:

      ipv6 isis accept adv-rtr <x.xx.xx> [enable] [i-sid <0-16777215>] [isid-list WORD<1-32>] [ [route-map WORD<1–64>]

   2. Configure an IPv6 IS-IS accept policy based on a particular I-SID:

      ipv6 isis accept i-sid <0-16777215> [enable] [route-map WORD<1–64>]

   3. Configure an IPv6 IS-IS accept policy based on a particular I-SID list:

      ipv6 isis accept isid-list WORD<1-32> [enable] [route-map WORD<1–64>]

   4. Specify a particular route-map to use for all IS-IS routes from all BEBs unless a more specific filter exists for the advertising BEB. :

      ipv6 isis accept route-map WORD<1–64>

5. Enable the configured IPv6 IS-IS accept policies:

   ipv6 isis accept [adv-rtr <x.xx.xx>] [i-sid <0-16777215>] [isid-list WORD<1-32>] enable

6. Exit to Global Configuration mode:

   exit

7. Apply the IPv6 IS-IS accept policy changes, which removes and re-adds all routes with updated filters:

   ipv6 isis apply accept [vrf WORD <1–16>]

Example

Configure an IPv6 IS-IS accept policy based on a particular I-SID:

Switch:1>enable
Switch:1#configure terminal
Switch:1(config)#router vrf vrftest
Switch:1(config-isis)#ipv6 isis accept i-sid 101 route-map test
Switch:1(config-isis)#ipv6 isis accept i-sid 101 enable
Switch:1#exit
Switch:1(config)#ipv6 isis apply accept