Specifying the source address of TCP connections
By default, BGP uses the primary IPv4/IPv6 address of the output interface in the optimal route to a peer or peer group as the source address of TCP connections to the peer or peer group.
Change the source address in the following scenarios:
If the peer's IPv4/IPv6 address belongs to an interface indirectly connected to the local router, 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 on the local end, and x.x.x.x is not the IPv4 address of interface B, you must do the following:
Use the peer connect-interface command on the peer.
Specify the interface whose IPv4 address is x.x.x.x as the source interface.
If the source interface fails on a BGP router that has multiple links to a peer, BGP must re-establish TCP connections. To avoid this problem, use a loopback interface as the source interface or use the IP address of a loopback interface as the source address.
If the BGP sessions use the IP addresses of different interfaces, specify a source address or source interface for each peer to establish multiple BGP sessions to a router. Specify a source address for each peer if the BGP sessions use the different addresses of the same interface. Otherwise, the local BGP router might fail to establish a TCP connection to a peer when it uses the optimal route to determine the source address.
To specify the source address of 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 IPv4 address of TCP connections to a peer or peer group. | peer ipv4-address [ mask-length ] source-address source-ipv4-address peer group-name source-address source-ipv4-address | The peer source-address command is available in Release 1121 and later. By default, BGP uses the primary IPv4 address of the output interface in the optimal route to a peer or peer group as the source address of TCP connections to the peer or peer group. |
4. Specify the source interface of TCP connections to a peer or peer group. | peer { group-name | ip-address [ mask-length ] } connect-interface interface-type interface-number |
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 IPv6 address of TCP connections to a peer or peer group. | peer ipv6-address [ prefix-length ] source-address source-ipv6-address peer group-name source-address source-ipv6-address | The peer source-address command is available in Release 1121 and later. By default, BGP uses the primary IPv6 address of the output interface in the optimal route to a peer or peer group as the source address of TCP connections to the peer or peer group. |
4. Specify the source interface for establishing TCP connections to a peer or peer group. | peer { group-name | ipv6-address [ prefix-length ] } connect-interface interface-type interface-number |