3Com 4200G, 4210, 5500, 5500G manual 12

12 DLDP CONFIGURATION GUIDE
Configuring DLDP Sometimes, unidirectional links may appear in networks. On a unidirectional link,
one end can receive packets from the other end but the other end cannot.
Unidirectional links can be caused by fiber cross-connection or fiber cut (including
single-fiber cut and lack of a fiber connection).
They can cause problems such as spanning tree topology loops.
You can use the Device Link Detection Protocol (DLDP) to monitor the link status of
optical fiber cables and copper twisted pairs such as super category 5 twisted
pairs. Once detecting a unidirectional link, DLDP shuts down the port or ask you to
do so depending on your configuration.
Network Diagram Figure18 Network diagram for DLDP configuration
Networking and
Configuration
Requirements
■Switch A and Switch B are connected through two pairs of fibers. The
connecting ports are operating in mandatory full duplex mode at 1000 Mbps.
Both of the switches support DLDP.
■Configure DLDP to automatically disconnect the detected unidirectional link.
■After the fibers are connected correctly, the port shut down by DLDP restores
automatically.
Applicable Products
Configuration Procedure ■Configure Switch A
SwitchB
SwitchA
PC
GE1/1/3
GE1/1/3 GE1/1/4
GE1/1/4
SwitchB
SwitchA
PC
GE1/1/3
GE1/1/3 GE1/1/4
GE1/1/4
SwitchB
SwitchA
PC
GE1/1/3
GE1/1/3 GE1/1/4
GE1/1/4
SwitchB
SwitchA
PC
GE1/1/3
GE1/1/3 GE1/1/4
GE1/1/4
Product series Software version Hardware version
Switch 5500 Release V03.02.04 All versions
Switch 5500G Release V03.02.04 All versions
Switch 4500 R elease V03.03.00 All versions