Configuring Trill; Overview; Basic Concepts; Trill Frame Formats - HP 6125XLG Configuration Manual

Configuring TRILL

Transparent Interconnect of Lots of Links (TRILL) uses IS-IS to provide transparent Layer 2 forwarding.

Overview

TRILL combines the simplicity and flexibility of Layer 2 switching with the stability, scalability, and rapid
convergence capability of Layer 3 routing. All these advantages make TRILL very suitable for large flat
Layer 2 networks in data centers.

Basic concepts

RBridge—Routing bridge (RB for short) that runs TRILL. RBs are classified into ingress RBs, transit RBs,
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and egress RBs, depending on their positions in the TRILL network. A frame enters the TRILL network
through an ingress RB, travels along transit RBs, and leaves the TRILL network through an egress RB,
as shown in
TRILL network—A Layer 2 network comprised of RBs, as shown in
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Nickname—Unique identifier of an RB in the TRILL network. TRILL automatically assigns nicknames
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to RBs.
• Link State Database—The LSDB contains all link state information in the TRILL network.
Link State Protocol Data Unit—An LSP describes local link state information and is advertised
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between neighbor devices.
Appointed VLAN-x Forwarder (AVF) and appointed port—TRILL supports VLANs. To avoid loops,
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TRILL requires all the traffic of a VLAN on a network segment to enter and leave the TRILL network
through the same port of an RB. The RB is the AVF of the VLAN, and the port is the appointed port.
Designated Routing Bridge—The DRB corresponds to the DIS in IS-IS. It helps simplify network
•
topology and appoints AVFs for VLANs on each RB.
For more information about LSDB, LSPDU, and DIS, see Layer 3—IP Routing Configuration Guide.

TRILL frame formats

TRILL frames include control frames and data frames.
TRILL control frames include TRILL Hello, LSP, CSNP, PSNP, MTU-prob, and MTU-ack. These control frames
use 802.1Q encapsulation, and have a fixed destination multicast address 0180-C200-0041.
TRILL data frames have a specific format, as shown in
header are added to the original Ethernet frame.
Figure 2.
Figure 1. A TRILL header and an outer Ethernet
1
Figure 3.