R3303-HP HSR6800 Routers High Availability Configuration Guide

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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 sho
ws 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.