Dldp Introduction; Dldp Fundamentals - H3C S5810 Series Operation Manual

Ethernet switches

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Figure 1-2 Unidirectional fiber link: a fiber not connected or disconnected

DLDP Introduction

The Device Link Detection Protocol (DLDP) can detect the link status of a fiber cable or twisted pair. On

detecting a unidirectional link, DLDP, as configured, can shut down the related port automatically or

prompt users to take actions to avoid network problems.

As a data link layer protocol, DLDP cooperates with physical layer protocols to monitor link status. While

the auto-negotiation mechanism provided by the physical layer detects physical signals and faults,

DLDP performs operations such as identifying peer devices, detecting unidirectional links, and shutting

down unreachable ports. The cooperation of physical layer protocols and DLDP ensures that

physical/logical unidirectional links can be detected and shut down and prevents failure of other

protocols such as STP. If both ends of a link are operating normally at the physical layer, DLDP detects

whether the link is correctly connected at the link layer and whether the two ends can exchange packets

properly. This is beyond the capability of the auto-negotiation mechanism at the physical layer.

DLDP link states

A device is in one of these DLDP link states: Initial, Inactive, Active, Advertisement, Probe, Disable, and

DelayDown, as described in

Table 1-1 DLDP link states

DLDP is disabled.

DLDP is enabled but the link is down.

DLDP is enabled and the link is up, or the neighbor entries have

been cleared.

All neighbors are bi-directionally reachable or DLDP has been in

active state for more than five seconds. This is a relatively state

where no unidirectional link has been detected.

Indicates...

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