IPv6 Multicast over MCT

Multicast state information is synchronized between the MCT peers using MP-BGP EVPN transport, specifically the Join Sync Route and the Leave Sync Route. Multicast protocol packets are sent on the peer link only when required.

MLD (Multicast Listener Discovery) protocol packets are of three types.

MLD query packet processing

Each EVI is associated with a multicast group ID (MGID) that is BUM-suppressed (Broadcast, unknown unicast and multicast). However, query packets need to be transmitted on an interchassis link (ICL) to address the following scenarios.
  • The querier connected to only one of the MCT peer switches is the elected querier.
  • Only one of the peer switches is configured as a querier.
  • The switch ages out MLD routes if memberships are not confirmed in the timeout interval. Although query packets are received on the MCT peer link, the mrouter port is not learned or considered on that peer link.

MLD membership reports

Duplicate MLD query packets on CCEP

If a query is configured on both MCT peers of a member VLAN, duplicate query packets reach clients that are connected to the MCT domain by means of a Cluster Client Edge Port (CCEP).

Multicast modules use inclusive multicast routes of EVPN NLRI to exchange the multicast querier configuration on the member VLANs. The MCT peer that is the DF of the member VLAN is elected as the querier.

Multicast modules handle querier election for the member VLAN when peer links are active or inactive.

MLD listener done

When fast-leave is not configured and an MCT peer receives MLD Listener Done from one of its clients for group G, the switch or router informs other MCT peers about the group-specific query and latency by using the Leave Sync Route. The peer switch, which runs the querier, sends group-specific queries and group queries.

Mrouter synchronization

Mrouter synchronization helps in achieving optimal path selection for unknown multicast traffic and optimal MP-BGP message exchange between MCT peers. The node that is elected multicast DF (designated forwarder) for the VLAN forwards data traffic on CCEP as an mrouter port.

Scalability

Scalability feature Maximum
MLD snooping-enabled VLANs or bridge domains over MCT 256
IPv6 PIM-enabled VEs over MCT 32
MLD groups over MCT 4000
IPv6 PIM cache routes over MCT 2000

Device support

Extreme Networks supports IPv6 multicast over MCT on the following devices.
  • ExtremeSwitching SLX 9540
  • ExtremeRouting SLX 9640