Unidirectional Link Detection

rdf:langString Unidirectional Link Detection

rdf:langString Unidirectional Link Detection (UDLD) is a data link layer protocol from Cisco Systems to monitor the physical configuration of the cables and detect unidirectional links. UDLD complements the Spanning Tree Protocol which is used to eliminate switching loops. * Unidirectional Link Detection (UDLD) is one of two major features (UDLD and loop guard) in Cisco Switches to prevent Layer 2 loops. * Spanning-Tree Protocol (STP) resolves redundant physical topology into a loop-free, tree-like forwarding topology via blocking one or more ports.However, Unidirectional Link failure can cause "traffic blackholing" and loops in the Switch topology. * In order to detect the unidirectional links before the forwarding loop is created, UDLD works by exchanging protocol packets between the neighboring devices. * In order for UDLD to work, both switch devices on the link must support UDLD and have it enabled on respective ports.