DHCPv6-relay multicast operations

  • A DHCPv6-relay message sent to any multicast address carries a hop limit of 32. The hop limit for DHCPv6 requests sent to a unicast address is determined by the ipv6 hop-limit 1 - 255 command at the global configuration level; Default: 64.

  • Multicast addresses reserved for DHCPv6 include the following:
    • FF02::1:2—All_DHCP_Relay_Agents_and_Servers

    • FF05::1:3—All_DHCP_Servers

  • DHCPv6 client and relay functions are mutually exclusive on a VLAN. Attempting to configure one of these functions on a VLAN while the other is already configured results in one of the following messages:
    • Cannot configure an IPv6 helper-address as DHCPv6 client is enabled on the VLAN
    • Cannot enable DHCPv6 client as an IPv6 helper-address is configured on the VLAN.
  • The routing switch supports concurrent, independent operation of DHCPv4 and DHCPv6.

  • Operating limits:

    DHCPv6-relay feature


    Unique helper addresses supported on the routing switch


    Unique helper addresses per VLAN interface



    If the same helper address is used on multiple VLANs, it is counted as one address toward these maximums.