Skip to main content

3. MLD Snooping Recommendations

The suggestions in this document are based on IGMP, which applies only to IPv4. For IPv6, Multicast Listener Discovery [MLD] must be used instead. Because MLD is based on IGMP, we do not repeat the entire description and recommendations for MLD snooping switches. Instead, we point out the few cases where there are differences from IGMP.

  1. The IPv6 protocol for multicast group maintenance is called Multicast Listener Discovery [MLDv2]. MLDv2 uses ICMPv6 message types instead of IGMP message types.
  2. Equivalent to the IPv4 behaviors regarding the null IP Source address, MLD membership reports must not be rejected by an MLD snooping switch because of an unspecified IP source address (::).
  3. Additionally, if a non-Querier switch spoofs any General Queries (as addressed in Section 2.1 above, for Spanning Tree topology changes), the switch should use the unspecified IP source address (::) when sending said queries. When such proxy queries are received, they must not be included in the Querier election process.
  4. The Initial allocation of IPv6 multicast addresses, as described in [RFC3307], however, covers only the lower 32 bits of group ID.
Last updated on