New Training: Customize Spanning Tree Protocol
In this 10-video skill, CBT Nuggets trainer Keith Barker teaches you how to configure and verify Spanning Tree Protocol (STP) features, including several STP guards. Learn how to configure and verify UplinkFast, BackboneFast, PortFast, and STP BPDU filtering. Gain an understanding of STP Root Guard, BPDU Guard, Loop Guard, and more. Watch this new Cisco training.
Watch the full course: Cisco CCNP Enterprise Core
This training includes:
1.2 hours of training
You’ll learn these topics in this skill:
Welcome to Customize STP
Unidirectional Link Detection (UDLD)
What is Unidirectional Link Detection (UDLD)?
Unidirectional Link Detection (UDLD) is a Cisco-proprietary layer 2 protocol that you can use to detect unidirectional links in your network. UDLD further deters issues that arise from unidirectional links, and it can help prevent forwarding loops and the blackholing of traffic, by identifying and handling logical one-way links that could otherwise go undetected.
When using UDLD, each switch port that has been configured for UDLD exchanges data about its device and port ID with that of its connected neighbor. Because of this, if the link is bi-directional, it should receive information about its own device and port ID from its neighbor. If it doesn't, the protocol determines that the link is unidirectional. This can occur when the link is up on both sides but one side is not receiving packets, or when wiring mistakes have occurred.
It should be noted that both ends of a link must support UDLD for the protocol to function correctly.