Specifying the source interface for TCP connections
By default, BGP uses the output interface of the optimal route to a peer or peer group as the source interface for establishing TCP connections to the peer or peer group, and it uses the IP address/IPv6 address of the output interface as the source IP address/IPv6 address of TCP connections. You can change the source interface in the following scenarios:
If the peer's IP address/IPv4 address belongs to an interface indirectly connected to the local router, you must specify that interface as the source interface for TCP connections on the peer. For example, interface A on the local end is directly connected to interface B on the peer. If you use the peer x.x.x.x as-number as-number command in which x.x.x.x is not the IP address of interface B on the local end, you must use the peer connect-interface command on the peer to specify the interface whose IP address is x.x.x.x as the source interface for establishing a TCP connection.
On a BGP router that has multiple links to a peer, if the source interface fails, BGP has to reestablish TCP connections. To avoid this problem, use a loopback interface as the source interface.
To establish multiple BGP sessions between two routers, specify the source interface for establishing TCP connections to each peer on the local router. Otherwise, the local BGP router might fail to establish a TCP connection to a peer when using the outbound interface of the best route to the peer as the source interface.
To specify the source interface for TCP connections (IPv4):
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter BGP view or BGP-VPN instance view. |
| N/A |
3. Specify the source interface for establishing TCP connections to a peer or peer group. | peer { group-name | ip-address } connect-interface interface-type interface-number | By default, BGP uses the outbound interface of the best route to the BGP peer or peer group as the source interface for establishing a TCP connection to the peer or peer group. |
To specify the source interface for TCP connections (IPv6):
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter BGP view or BGP-VPN instance view. |
| N/A |
3. Specify the source interface for establishing TCP connections to a peer or peer group. | peer { group-name | ipv6-address } connect-interface interface-type interface-number | By default, BGP uses the outbound interface of the best route to the BGP peer or peer group as the source interface for establishing a TCP connection to the peer or peer group. |