3Com Switch 7750 Configuration Guide

212 CHAPTER 27: DLDP CONFIGURATION

Figure 56 Fiber broken or not connected

DLDP provides the following features:

■ As a link layer protocol, it works together with the physical layer protocols to

monitor the link status of a device.

■ The auto-negotiation mechanism at the physical layer detects physical signals

and faults. DLDP identifies peer devices and unidirectional links, and disables

unreachable ports.

■ Even if both ends of links can work normally at the physical layer, DLDP can

detect whether these links are connected correctly and whether packets can be

exchanged normally at both ends. However, the auto-negotiation mechanism

cannot implement this detection.

■ In order for DLDP to detect fiber disconnection in one direction, you need to

configure the port to work in mandatory full duplex mode at a mandatory rate.

■ When the port determines the duplex mode and speed through

auto-negotiation, even if DLDP is enabled, it does not take effect when the

fiber in one direction is disconnected. In this case, the port is considered down.

DLDP Fundamentals

DLDP Implementation DLDP detects link status by exchanging the following types of packets.

SwitchB

SwitchA

GE2/0/3

GE2/0/4

SwitchB

SwitchA

GE2/0/3

GE2/0/4