This video (http://youtu.be/ivXCDghnjTM) discusses the theory and demonstrates the configuration of the Unidirectional Link Detection (UDLD) feature found on Cisco Catalyst switches.
This video is a sample from the "SWITCH (300-115) Complete Video Course" by Kevin Wallace, available from Cisco Press.
Get the ROUTE 300-101 Complete Video Course here: http://kwtrain.com/routecourse
Get the SWITCH 300-115 Complete Video Course here: http://kwtrain.com/switchcourse
Get the TSHOOT 300-135 Complete Vid
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