HP 6125XLG R2306-HP 6125XLG Blade Switch TRILL Configuration Guide - Page 7

Multi-destination frame forwarding mechanism In a TRILL network, RBs compute a distribution tree for each VLAN according to the LSDB and use the distribution tree to guide the forwarding of multi-destination frames, which include multicast, broadcast, and unknown unicast frames in the VLAN. As shown in Figure 3, when a multicast frame from VLAN 10 enters the TRILL network, RB 1, which is an ingress RB, encapsulates the multicast frame into a TRILL frame. In the frame, the egress RB is RB 2, the root bridge of the distribution tree for VLAN 10. When the frame arrives at the root bridge, it is distributed throughout the distribution tree. Then, the TRILL frame is decapsulated by RB 3 and sent to the destination station S2. Because the network segment where RB 4 resides does not have a receiver of this frame, RB 4 drops the frame. Figure 3 Multicast frame forwarding flow VLAN 200 TRILL network RB 4 S1 RB 1 VLAN 10 RB 3 S2 VLAN 10 RB 2 Inner D-MAC = Multi Inner S-MAC = S1 Inner VLAN = 10 Payload Ethernet frame Outer D-MAC = All RBs Outer S-MAC = RB 1 Outer VLAN = 200 Egress RB = RB 2 Ingress RB = RB 1 Inner D-MAC = Multi Inner S-MAC = S1 Inner VLAN = 10 Payload TRILL frame Outer D-MAC = All RBs Outer S-MAC = RB 2 Outer VLAN = 200 Egress RB = RB 2 Ingress RB = RB 1 Inner D-MAC = Multi Inner S-MAC = S1 Inner VLAN = 10 Payload TRILL frame Inner D-MAC = Multi Inner S-MAC = S1 Inner VLAN = 10 Payload Ethernet frame Multicast frame Distribution tree of VLAN 10 Root bridge of distribution tree Leaf of distribution tree Protocols and standards • RFC 6325: Routing Bridges (RBridges): Base Protocol Specification • RFC 6326: Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS • RFC 6327: Routing Bridges (RBridges): Adjacency • RFC 1195: Use of OSI IS-IS for Routing in TCP/IP and Dual Environments 4