Configuring IS-IS route filtering
You can use an ACL, IP prefix list, or routing policy to filter routes calculated using received LSPs and routes redistributed from other routing protocols.
Filtering routes calculated from received LSPs
IS-IS saves LSPs received from neighbors in the LSDB, and uses the SPF algorithm to calculate the shortest path tree with itself as the root. IS-IS installs the calculated routes to the IS-IS routing table and the optimal routes to the IP routing table.
Perform this task to filter calculated routes. Only routes that are not filtered can be added to the IP routing table. The filtered routes retain in the IS-IS routing table and can be advertised to neighbors.
To filter routes calculated using received LSPs:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter IS-IS IPv4 unicast address family view. | isis [ process-id ] [ vpn-instance vpn-instance-name ] cost-style { wide | wide-compatible } address-family ipv4 [ unicast ] | N/A |
3. Filter routes calculated using received LSPs. | filter-policy { ipv4-acl-number | prefix-list prefix-list-name | route-policy route-policy-name } import | By default, IS-IS route filtering is not configured. |
Filtering redistributed routes
IS-IS can redistribute routes from other routing protocols or other IS-IS processes, add them to the IS-IS routing table, and advertise them in LSPs.
Perform this task to filter redistributed routes. Only routes that are not filtered can be added to the IS-IS routing table and advertised to neighbors.
To filter redistributed routes:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter IS-IS IPv4 unicast address family view. | isis [ process-id ] [ vpn-instance vpn-instance-name ] cost-style { wide | wide-compatible } address-family ipv4 [ unicast ] | N/A |
3. Filter routes redistributed from other routing protocols or IS-IS processes. | filter-policy { ipv4-acl-number | prefix-list prefix-list-name | route-policy route-policy-name } export [ protocol [ process-id ] ] | By default, IS-IS route filtering is not configured. |