IPv6 DHCP Relay Switch Side Troubleshooting

With DHCP Relay, the switch only participates in forwarding the requests and replies to and from the client and the DHCP server. The switch always acts as the relay agent, on which you configure the forward path to the server.

To troubleshoot DHCP Relay issues on the switch, use the following procedure.

Procedure

  1. Verify that the DHCP server is reachable using ping. If ping is working and the DHCP server is reachable, DHCP should work.
  2. Verify that the relay agents and the forward path configured are reachable. Ping the server and the gateway to the server.
  3. Check that the relay agent configurations are correct. Also verify that DHCP is enabled on the switch:

    show ipv6 dhcp-relay interface {gigabitEthernet {slot/port[/sub-port][-slot/port[/sub-port]][,...]}|vlan <1-4059>

  4. Verify that IPv6 forwarding is enabled globally:

    show ipv6 global

  5. Verify that the IPv6 based VLAN where the DHCP relay agent is configured is enabled:

    show ipv6 interface vlan <1-4059>

  6. In a scenario with VRRP and SMLT, configure VRRP IP as the DHCP relay agent.
  7. When using the VRRP VRID as the relay agent, make sure the VRRP configurations are proper.
  8. To verify that relay forward and relay receive are working, enable trace for DHCP with IPv6, and grep trace for relay:

    trace level 66 3

    trace grep relay

    trace screen enable

  9. Display the count of DHCP Relay requests and replies to verify the system received requests and replies:

    show ipv6 dhcp-relay counters