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Configuration Guide - DCN and Server Management

CloudEngine 8800, 7800, 6800, and 5800 V200R003C00

This document describes the configurations of Trill, FCoE, DCB, and NLB Server Cluster Association.
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Basic Concepts

Basic Concepts

This section introduces basic concepts about Transparent Interconnection of Lots of Links (TRILL). Figure 1-1 shows basic roles in the typical TRILL networking.
Figure 1-1 Large-scale Layer 2 TRILL networking

Devices in TRILL Networking


Router bridge (RB) is a Layer 2 switch running TRILL. RBs are classified into ingress RB, transit RB, and egress RB according to their locations on a TRILL network. An ingress RB indicates the ingress from which packets enter the TRILL network. A transit RB indicates the intermediate node through which packets pass on the TRILL network. An egress RB indicates the egress from which packets leave the TRILL network.


A designated routing bridge (DRB) is an RB that functions as a transit device and performs special tasks on TRILL networks. On a TRILL broadcast network, if two RBs are located on the same virtual local area network (VLAN), the RB whose interface with a higher DRB priority or larger MAC address is selected as the DRB when they are establishing neighbor relationships. The DRB communicates with each device on the network to synchronize all the link state databases (LSDBs) on the VLAN, sparing every two devices from communicating for LSDB synchronization. DRBs perform the following tasks:
  • Generate pseudonode link state protocol data units (LSPs) when more than two RBs exist on the network.
  • Send complete sequence number protocol data units (CSNPs) to synchronize LSDBs.
  • Select a carrier VLAN as the Designated VLAN, the DVLAN will transmit user packets and TRILL control packets.
  • Select the appointed forwarder (AF). Only one RB can function as the AF for a customer edge (CE) VLAN.


An AF is an RB elected by the DRB to forward user traffic. Non-AF RBs cannot forward user traffic. As shown in Figure 1-1, loops may occur if a server is dual-homed to a TRILL network but does not have double network adapters working in load balancing mode. Therefore, an RB must be elected to forward user traffic.

VLANs on a TRILL Network

Table 1-2 VLANs on a TRILL network



Packet Supported


A CE VLAN connects to the TRILL network and is usually configured on the edge devices of a TRILL network to generate multicast routes.

Native Ethernet packets

Admin VLAN

A special CE VLAN transmits TRILL network management traffic.

TRILL network management traffic.

Carrier VLAN

A carrier VLAN transmits TRILL control packets and TRILL data packets. A maximum of three carrier VLANs can be configured on an RB. In the inbound direction, native Ethernet packets are encapsulated into TRILL packets in carrier VLANs. In the outbound direction, TRILL packets are decapsulated and restore to native Ethernet packets.

TRILL control packets and data packets

Designated VLAN

To combine or separate TRILL networks, multiple carrier VLANs are configured on a TRILL network. However, only one carrier VLAN is selected to forward TRILL control and data packets. The selected VLAN is called a designated VLAN.

TRILL control packets and data packets


Each RB on a TRILL network has a unique nickname. The nickname is similar to an IP address in terms of function.

A nickname has one priority and one root priority.
  • When a nickname conflict occurs on a TRILL network, the priority determines which RB's nickname is to be advertised to other RBs.
    1. The RB with the highest priority advertises its nickname.
    2. If the RBs with the same nickname have the same priority, the RB with the largest system ID advertises its nickname.
  • An RB uses its root priority to run for the root of multicast tree. The RBs with the highest and second-highest root priority are selected as the roots of two multicast trees.

Interface Roles

Interfaces of switches on TRILL networks are classified into the following types:
  • Trunk interfaces: connect switches and transmit TRILL data packets and protocol packets only.
  • Access interfaces: transmit Native Ethernet packets and protocol packets only.
  • Hybrid interfaces: transmit both TRILL data and protocol packets and Native Ethernet packets by default.
  • P2P port: On a P2P network, the ports between two RBs are P2P ports. P2P ports are special trunk ports, and switches connected using the P2P ports do not participate in DRB election.

By default, the type of TRILL interfaces is p2p.


Similar to IS-IS, TRILL uses network entity titles (NETs) to identify network layer information about switches. A NET includes the following elements:
  • Area ID: An area ID identifies an area. An IS-IS network has multiple areas, while a TRILL network has only one area. The TRILL area ID is 00.

  • System ID: identifies a host or switch and has a fixed length of 48 bits.

    In actual applications, a system ID can be automatically generated or configured. You can specify the system ID (unique on the entire network) when using the network-entity (TRILL) command to configure a NET. If this command is not configured, the system generates a system ID. The generated system ID is the same as the bridge MAC address of RB.

  • SEL (also referred to as NSAP Selector or N-SEL): The role of a SEL is similar to that of the protocol identifier of IP. Each transport protocol has one unique SEL. The SEL of TRILL is 00.
Updated: 2019-05-08

Document ID: EDOC1100004349

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