H3C Technologies H3C S6800 Series Switches - Manual (Page 13)

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Figure 5 TRILL Layer 3 forwarding
A TRILL VR contains multiple member RBs that are configured with the same virtual IP address. All
member RBs participate in Layer 3 forwarding. A master RB responds to ARP or ND requests. The master
RB is elected by using the following rules:
• The member RB with the highest priority is elected as the master RB. The master election priority is
64 by default, and it is not configurable.
• If member RBs have the same priority, the member RB with the highest system ID is elected.
TRILL uses the following mechanisms to forward Layer 3 traffic:
• Unicast traffic forwarding mechanism—Access RBs forward original unicast frames to the TRILL VR.
Member RBs of the VR then perform Layer 3 forwarding for the frames.
• Multidestination traffic forwarding mechanism—To forward multidestination traffic, you must
enable IGMP/MLD snooping and dropping unknown multicast data on all RBs. In this way, router
ports and member ports in Layer 2 multicast forwarding entries are appointed along TRILL
distribution trees. Access RBs forward original multidestination frames to the TRILL VR through TRILL
distribution trees. Member RBs of the VR then perform Layer 3 forwarding for the frames.
Each VLAN supports only one TRILL distribution tree. If you configure multiple distribution trees for
a VLAN, the distribution tree with the lowest root nickname takes effect.
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