UDLD
UDLD detects unidirectional link failures on fiber/copper to prevent loops and blackholes.
Updated: 2026-03-06
Definition
Unidirectional Link Detection (UDLD) detects when traffic flows only one way on a link.
It can disable a link to prevent loops or connectivity issues caused by one-way failures.
Key points
- Detects one-way links
- Helps prevent loops/blackholes
- Often used on fiber uplinks
Common mistakes
- Ignoring one-way link failures (hard to troubleshoot).
- Not using link protection features on critical uplinks.
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