The interface index for the interface from which the source address for session is chosen. If non-zero, BGP will look for the first address on this interface with a type matching bgpPeerRemoteAddrType, and use that as the source address. If no matching address or interface exists, or this field is set to zero, the source address is chosen as described in bgpPeerLocalAddr. This field is ignored for peers identified only by interface (bgpPeerLocalAddr and bgpPeerRemoteAddr are both zero). This field can be changed at any time, causing the peer to be immediately deactivated and reactivated. If the configured interface (or address on that interface) did not exist when the peer was activated, and is subsequently added, the peer will automatically use the configured interface address. This will cause the peer to be immediately deactivated and reactivated.