Protocols And Standards - HP 6125XLG Configuration Manual

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
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
S1
VLAN 10
Inner D-MAC = Multi
Inner S-MAC = S1
Inner VLAN = 10
Payload
Ethernet frame

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 1 195: Use of OSI IS-IS for Routing in TCP/IP and Dual Environments
•
Figure 3, when a multicast frame from VLAN 10 enters the TRILL network, RB 1, which is an
VLAN 200
TRILL network
RB 1
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
Multicast frame
RB 4
RB 2
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
Distribution tree
of VLAN 10
4
RB 3
VLAN 10
Inner D-MAC = Multi
Inner S-MAC = S1
Inner VLAN = 10
Payload
Ethernet frame
Root bridge of Leaf of
distribution tree distribution tree
S2