R3102-R3103-HP 6600/HSR6600 Routers High Availability Configuration Guide

Configuring DLDP

DLDP is supported only when the SAP module is operating in bridge mode.

Overview

Unidirectional links occur when only one end of a bidirectional link can receive packets.

Unidirectional links cause problems such as loops in an STP-enabled network.

For example, the link between two switches, Switch A and Switch B, is a bidirectional link when they

are connected through a fiber pair, with one fiber used for sending packets from A to B and the other

for sending packets from B to A. This link is a two-way link. When one of the fibers stops working, the

link becomes a unidirectional link (one-way link).

Unidirectional fiber links through the following types:

 Cross-connected.

 Disconnected at one end or one fiber of a fiber pair is broken.

Figure 7 shows a correct fiber connection and the two types of unidirectional fiber connections.

Figure 7 Correct and incorrect fiber connections

The device link detection protocol (DLDP) detects unidirectional links (fiber links or twisted-pair links)

and can be configured to shut down the faulty port automatically or prompt users to take actions to

avoid network problems.

Correct fiber connection

Unidirectional connection type 1

Cross-connected fibers

Unidirectional connection type 2

One fiber of a fiber pair is not

connected or is broken

GE3/0/1

GE3/0/2

Router A

Router B

GE3/0/1

GE3/0/2

Router A

Router B

GE3/0/1

GE3/0/2

Router A

Router B

Ethernet

fiber port

Unconnected or broken fiberFiber linkTx end Rx end