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 heavily burdens devices. To address this problem, you can configure devices to advertise only the routes that they 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 the BGP device to filter the routes advertised by all its peers or peer groups.
You can configure a BGP device to filter routes to be advertised.
1. Run system-view
  The system view is displayed.
2. Run bgp { as-number-plain | as-number-dot }
  The BGP view is displayed.
3. Enter the corresponding address family view based on network type to configure BGP devices on networks.
  - Run ipv4-family { unicast | multicast }
    
    The IPv4 address family view is displayed.
  - Run ipv6-family [ unicast ]
    
    The IPv6 address family view is displayed.
4. 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.
Configure BGP to filter the routes advertised by a specified peer or peer group.
1. Run system-view
  The system view is displayed.
2. Run bgp { as-number-plain | as-number-dot }
  The BGP view is displayed.
3. Enter the corresponding address family view based on network type to configure BGP devices on networks.
  - Run ipv4-family { unicast | multicast }
    
    The IPv4 address family view is displayed.
  - Run ipv6-family [ unicast ]
    
    The IPv6 address family view is displayed.
4. 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 | ipv4-address | 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.