Configuring Trill; Overview; Basic Concepts; Trill Frame Formats - HP 6125XLG Trill 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) that runs TRILL. RBs are classified into ingress RBs, transit RBs, 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
•
• System ID—Unique identifier of an RB in the TRILL network. The system ID is 6-byte.
Nickname—Address of an RB in the TRILL network. The nickname is 2-byte.
•
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
•
between neighbor devices.
Designated Routing Bridge (DRB)—Similar to the designated IS (DIS) in IS-IS, a DRB exists in the
•
broadcast network. It helps simplify network topology, and appoints AVFs and appointed ports for
the VLANs on each RB in the broadcast network.
• Appointed VLAN-x Forwarder (AVF) and appointed port—To avoid loops, TRILL requires all the
traffic of a VLAN on a broadcast network 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.
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-probe, 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.