In data center (DC) applications, Ethernet VPN (EVPN) is used to standardize inter-PoD communication for both intra-DC and inter-DC applications.
A subnet can span multiple points of delivery (PoD) and DCs. EVPN provides a robust multitenant solution with extensive multihoming capabilities to stretch a subnet (VLAN) across multiple PoDs and DCs. Many hosts or VMs (up to several hundred) can be attached to a subnet that is stretched across several PoDs and DCs.
Hosts or VMs express their interest in multicast groups on a subnet or VLAN by sending IGMP membership reports (Joins) for their interested multicast groups. Also, an IGMP router (for example, IGMPv1) periodically sends membership queries to determine whether any hosts on that subnet still want to receive multicast traffic for that group.
The ARP (Address Resolution Protocol) and NDP (Network Discovery Protocol) suppression mechanism in EVPN reduces the flooding of ARP messages over EVPN. Reducing the flood of IGMP messages (both Queries and Reports) over EVPN is achieved through IGMP Join Sync and IGMP Leave Sync routes as specified in the IETF draft IGMP and MLD Proxy for EVPN.
| EVPN route type | Route name | Purpose |
|---|---|---|
| 7 | IGMP Join Sync Route | To exchange (S,G)/(*,G) learned on BGP EVPN peers. |
| 8 | IGMP Leave Sync Route | To exchange group leave between BGP EVPN peers. |