Configuring Optimized Layer 2 Overlay Multicast Restrictions for Optimized Layer 2 Overlay Multicast, on page 1 Information About Optimized Layer 2 Overlay Multicast, on page 1 How to Configure Optimized Layer 2 Overlay Multicast, on page 5 Verifying Optimized Layer 2 Overlay Multicast on VTEP and Centralized Gateway, on page 9 Configuration Examples for Optimized Layer 2 Overlay Multicast, on page 10 Restrictions for Optimized Layer 2 Overlay Multicast • This feature does not support data MDT in the underlay. • Optimized Layer 2 overlay multicast source specific forwarding (S,G) is not supported. Only (*,G) is supported.
• Optimized Layer 2 overlay multicast is ineffective for a Distributed Anycast Gateway deployment (use Layer 3 Tenant Routed Multicast in a Distributed Anycast Gateway deployment). Optimized Layer 2 overlay multicast is applicable between Layer 2 Leaf or Centralized Gateway that extends the bridge-domain over EVPN VXLAN fabric. • Optimized Layer 2 overlay multicast handoff to Layer 3 tenant routed multicast (TRM) within the EVPN fabric is not supported. Information About Optimized Layer 2 Overlay Multicast Optimized Layer 2 Overlay Multicast functionality is based on IGMP or MLD Proxy for EVPN, as defined in draft-ietf-bess-evpn-igmp-mld-proxy .
In a BGP EVPN VXLAN fabric, there can be many hosts attached to a VLAN that is stretched across several sites. These hosts send IGMP membership reports to join their interested multicast groups. Also, the IGMP router periodically sends membership queries to find out if there are hosts on a VLAN that are interested in receiving multicast traffic for that group. This leads to a flooding of IGMP reports and queries in the overlay network across multiple sites. The network may have few hosts but the IGMP messages are sent to all VTEPs, resulting in an overloading of the fabric. This necessitates an IGMP or MLD Proxy to efficiently forward the multicast traffic.
When you enable an IGMP or MLD Proxy on the VTEP, the proxy forwards the multicast traffic only to the interested receivers, thus optimizing the bandwidth of the fabric. Configuring Optimized Layer 2 Overlay Multicast 1