Operation Manual – DLDPH3C S9500 Series Routing Switches Chapter 1 DLDP Configuration1-2Switch AGE2/1/1 GE2/1/2Switch BGE2/1/1 GE2/1/2PCFigure 1-2 Unidirectional fiber link: fiber not connected or disconnectedAs a data link layer protocol, DLDP cooperates with physical layer protocols to monitorthe link status of a device. While the auto-negotiation mechanism provided by thephysical layer detects physical signals and faults, DLDP performs operations such asidentifying peer devices, detecting unidirectional links, and shutting down unreachableports.The cooperation of the physical layer and DLDP ensures that physical/logicalunidirectional links be detected and shut down, thus preventing protocols such as STPfrom becoming ineffective.If the two sides of a link operate properly at the physical layer, DLDP checks whetherthe link is correctly connected and packets are exchanged properly at the data link layer.Such detection is impossible with the auto-negotiation mechanism of the physical layer.Ports shut down by DLDP due to unidirectional links detected can be brought upautomatically if the links restore to bidirectional links.Note:Do not configure a DLDP-enabled port as a loopback port.1.1.1 DLDP FundamentalsI. DLDP statesA device can operate in these DLDP states: initial, inactive, active, advertisement,probe, and disable.
