Controlling the Advertisement of BGP Routes
Context
There are usually a large number of routes in a BGP routing table. Transmitting a great deal of routing information brings a heavy load to devices. Routes to be advertised need to be controlled to address this problem. You can configure devices to advertise only routes that these devices want to advertise or routes that their peers require. Multiple routes to the same destination may exist and traverse different ASs. Routes to be advertised need to be filtered in order to direct routes to specific ASs.
Procedure
- Configure a BGP device to advertise routes to all peers
or peer groups.
You can configure a BGP device to filter routes to be advertised.
- Perform either of the following operations to configure
the BGP device to advertise routes to all peers or peer groups:
- To filter routes based on an ACL, run the filter-policy { acl-number | acl-name acl-name } export [ protocol [ process-id ] ] or the filter-policy { acl6-number | acl6-name acl6-name } export [ protocol [ process-id ] ] command.
- To filter routes based on an IP prefix list, run the filter-policy ip-prefix ip-prefix-name export [ protocol [ process-id ] ] or the filter-policy ipv6-prefix ipv6-prefix-name export [ protocol [ process-id ] ] command.
If an ACL has been referenced in the filter-policy command but no VPN instance is specified in the ACL rule, BGP will filter routes including public and private network routes in all address families. If a VPN instance is specified in the ACL rule, only the data traffic from the VPN instance will be filtered, and no route of this VPN instance will be filtered.
- Perform either of the following operations to configure
the BGP device to advertise routes to all peers or peer groups:
- Configure a BGP device to advertise routes to a specific
peer or peer group.
- Perform any of the following operations to configure
the BGP device to advertise routes to a specific peer or peer group:
To filter routes based on an ACL, run the peer { group-name | ipv4-address | ipv6-address } filter-policy { acl-number | acl-name acl-name | acl6-number | acl6-name acl6-name } export command.
To filter routes based on an IP prefix list, run the peer { ipv4-address | group-name } ip-prefix ip-prefix-name export or the peer { group-name | ipv6-address } ipv6-prefix ipv6-prefix-name export command.
To filter routes based on an AS_Path filter, run the peer { ipv4-address | group-name | ipv6-address } as-path-filter { as-path-filter-number | as-path-filter-name } export command.
To filter routes based on a route-policy, run the peer { ipv4-address | group-name | ipv6-address } route-policy route-policy-name export command.
The routing policy applied in the peer route-policy export command does not support a specific interface as one matching rule. That is, the routing policy does not support the if-match interface command.
- Perform any of the following operations to configure
the BGP device to advertise routes to a specific peer or peer group:
