Tenant Routed Multicast in VXLAN Fabric

This chapter introduces the “Tenant Routed Multicast” (TRM) solution in BGP EVPN VXLAN fabric. TRM relies on standard-based BGP IPv4 MVPN Address-Family [RFC 6513] and [RFC 6514]. Figure 19-1 illustrates the basic idea of TRM operation. (1) Leaf switches establish a Multicast tunnel per tenant, which they are using for forwarding tenant-specific Intra/Inter-VN Multicast traffic. (2) When Leaf -101 starts receiving Multicast flow from host Cafe to group 239.77.77.77, it updates its tenant specific MRIB table and generates an MVPN route-type 5 “Source Active Auto-Discovery (SA A-D)” route, where the MP-REACH-NLRI carries information about Source-Specific group (S, G). This route-type is used for discovering if there are any Multicast receivers behind remote leafs. When Leaf-102 receives the BGP Update message, it imports information into the BGP table. (3) Next, host Bebe sends an IGMP join message. (5) Leaf-102 updates its MRIB and then it generates the MVPN route-type 7 “Source-Tree Join” route. By doing this, it informs the source that it has local receivers for Multicast group 239.77.77.77. Leaf-101 installs the route into BGP table and updates its MRIB by adding the NVE interface into group-specific OIL. Then it starts forwarding Multicast flow received from host Cafe to the core over Source-Specific Multicast delivery tree which is actually tunneled over tenant-specific Multicast tunnel. In other words, the destination IP address in outer IP header use Multicast tunnel-group address 238.101.102.103 and the source IP address is taken from interface NVE1. By doing this, the actual tenant-specific Inter-VNI Multicast flows are totally transparent to the Spine switch.

This chapter starts by explaining how Multicast tunnels used for Intra-VN (L2), and Inter-VN (L3) are established and how MRIB is constructed. Then it introduces the configuration required for TRM. The last two-section discusses BGP MVPN Control Plane operation and Multicast data forwarding Data Plane operation.

Figure-19-1: Tenant Routed Multicast (TRM) Topology.

The rest 35 pages can be read from my VXLAN book "VXLAN-A Practical guide to VXLAN" published in Leanpub.com