3Com 7757 Configuration Manual

Also see for Switch 7754: Product guide Datasheet Datasheet Installation guide Product guide

Contents

3Com 7757 Configuration Manual Manual pdf 211 page image

27 DLDP C ONFIGURATIONOverviewIntroduction You may have encountered unidirectional links in networking. When aunidirectional link occurs, the local device can receive packets from the peer devicethrough the link layer, but the peer device cannot receive packets from the localdevice. Unidirectional link can cause problems such as spanning tree protocol (STP)loops.Unidirectional links can be caused by■ Fiber cross-connection, as shown in Figure 55■ Fibers that are not connected or disconnected, as shown in Figure 56, thehollow lines in which refer to fibers that are not connected or disconnected.Device link detection protocol (DLDP) can detect the link status of an optical fibercable or copper twisted pair (such as super category 5 twisted pair). If DLDP finds aunidirectional link, it disables the related port automatically or prompts you todisable it manually according to the configurations, to avoid network problems.Figure 55 Fiber cross-connectionSwitchBSwitchAPCGE2/0/3GE2/0/3 GE2/0/4GE2/0/4SwitchBSwitchAPCGE2/0/3GE2/0/3 GE2/0/4GE2/0/4