Unidirectional Link Detection: Difference between revisions

Revision as of 15:16, 14 June 2019

Revision as of 00:45, 23 June 2019

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:* 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 looploops 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.