Hi all, I notice below description in user guide, my understand is source address mainly used for BGP session for TCP connection ,don't understand why this source is also used as next_hop_addr calculation. If source address is related with next hop calculation, this case is may not support: used MP_REACH_NLRI to support IPV4 route with IPV4 next hop ,but TCP connection type is IPV6. Since to support MP_REACH_NLRI for ipv4 channel, need to enabled ext_next_hop, if enabled ext_next_hop, if ipv6 source address is selected as next_hop_addr if no others configuration for next_hop_addr. Does my understand is correct ? source address ip Define local address we should use for next hop calculation and as a source address for the BGP session. Default: the address of the local end of the interface our neighbor is connected to. Thanks Arvin