Uni-Directional Link Detection detects links where either the transmit or receive path has failed. Used to monitor fibre-optic or twisted pair cabling for unidirectional links.
UDLD used periodic hello packets and uses the concept of echos to ensure neighbors are receiving UDLD the UDLD hellos.
Supports 2 modes of operations,
- Normal – Port is placed into undetermined state. Port is not shutdown.
- Aggressive – Tries to get echo by sending hellow 8 times. Then places the interface into errdisable.
Globally
Disabled by default,
SW1(config) # udld enabled
Per Interface
(fibre and copper)
SW1(config-if)# udld port aggressive
UDLD Neighbors
SW1# show udld neigh
Rick Donato is a Network Automation Architect/Evangelist and the founder of Packet Coders.
Latest posts by Rick Donato (see all)
- How to Configure a BIND Server on Ubuntu - March 15, 2018
- What is a BGP Confederation? - March 6, 2018
- Cisco – What is BGP ORF (Outbound Route Filtering)? - March 5, 2018
Want to become a networking expert?
Here is our hand-picked selection of the best courses you can find online:
Cisco CCNA 200-301 Certification Gold Bootcamp
Complete Cyber Security Course – Network Security
Internet Security Deep Dive course
Python Pro Bootcamp
and our recommended certification practice exams:
AlphaPrep Practice Tests - Free Trial