Question

A branch router acts as a DHCPv6 relay for clients on interface GigabitEthernet0/1. The centralized DHCPv6 server sits at 2001:DB8:100::10, reachable via a WAN link. Clients send SOLICIT messages (verified with debug), but they never receive an ADVERTISE. On the relay you see the config: 'ipv6 dhcp relay destination FE80::1'. The WAN interface toward the server is GigabitEthernet0/0. What is the most likely cause of the failure?

Accepted Answer

The relay destination is a link-local address configured without specifying the outgoing interface, so the relay cannot forward the RELAY-FORWARD message toward the remote server

Answer

DHCPv6 relay requires the 'ipv6 dhcp relay destination' command to reference the client-facing interface, not the server address

Answer

The clients must be configured with 'ipv6 address dhcp' before the relay will process SOLICIT messages

Answer

DHCPv6 relay uses the all-DHCP-servers multicast address FF05::1:3 automatically, so no destination command should be present