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Bring performance and reliability to your network with the HPE Aruba Networking Core, Aggregation, and Access layer switches. Discuss the latest features and functionality of your switching devices, and find ways to improve security across your network to bring together a mobile-first solution
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  • 1.  UDLD vs. DLDP

    Posted Nov 29, 2023 06:49 AM

    May someone explain the different please

    From the manuals:

    • "Uni-directional link detection (UDLD) monitors a link between two switches and blocks the ports on both
      ends of the link if the link fails at any point between the two devices."
    • "Device link detection protocol (DLDP) is switch technology that detects any unidirectional link failures that can occur in a network."
    • Upon detecting a link failure, the link PHY will be kept UP and will be blocked in the hardware.
    • All the upper layer protocols of the switch software (STP, LACP, etc.) will see the interface as DOWN.


  • 2.  RE: UDLD vs. DLDP

    Posted Nov 30, 2023 08:24 AM

    To my knowledge, UDLD is a Cisco proprietary protocol. It is described in an informational RFC 5171, contrary of what you might find it is not a standard:

    This document describes a Cisco Systems protocol that can be used to detect and disable unidirectional Ethernet fiber or copper links caused, for instance by mis-wiring of fiber strands, interface
       malfunctions, media converters' faults, etc.  It operates at Layer 2
       in conjunction with IEEE 802.3's existing Layer 1 fault detection

    HPE uses the term DLDP for the exact same functionality as UDLD, I have not tested it but it might be fun to do a packet capture of UDLD and DLDP and see what the difference is.

  • 3.  RE: UDLD vs. DLDP
    Best Answer

    Posted Dec 05, 2023 03:18 PM
      |   view attached

    Both protocols are used to identify unidirectional links but are not interoperable. The devices of each side of the link must be configured to use the same protocol. The below table gives you an overview which switch os will support what protocol. DLPD was originally the Comware OS implementation which was later implemented in AOS-S switches too that those work together.