The dhcpv6 relay source-interface command configures the IP address of a specified interface as the source IP address used by a DHCPv6 relay agent to forward packets.
The undo dhcpv6 relay source-interface command cancels the configuration of setting the IP address of a specified interface to the source IP address used by a DHCPv6 relay agent to forward packets.
By default, a DHCPv6 relay agent uses the IPv6 address of the outbound interface as the source IPv6 address of DHCPv6 packets.