Table of Contents

1 DLDP Configuration Guide· 1-1

Overview· 1-1

DLDP Introduction· 1-1

Configuring DLDP· 1-2

Network Diagram·· 1-2

Networking and Configuration Requirements· 1-2

Applicable Product Matrix· 1-2

Configuration Procedure· 1-2

Complete Configuration· 1-4

Configuration Guidelines· 1-4

 

Overview

DLDP Introduction

Sometimes, unidirectional links may appear in networks. On a unidirectional link, one end can receive packets from the other end but the other end cannot. Unidirectional links result in problems such as loops in an STP-enabled network.

As for fiber links, two kinds of unidirectional links exist. One occurs when fibers are cross-connected, as shown in 0. The other occurs when one end of a fiber is not connected or one fiber of a fiber pair gets disconnected, as illustrated by the hollow arrows in 0.

Figure 1-1 Unidirectional fiber link: cross-connected fiber

 

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

 

Device Link Detection Protocol (DLDP) can detect the link status of a fiber cable or twisted pair. On detecting a unidirectional link, DLDP can shut down the related port automatically or prompt users to take measures as configured to avoid network problems.

Configuring DLDP

Network Diagram

Figure 1-3 Network diagram for DLDP configuration

 

Networking and Configuration Requirements

l          Device A and Device B are connected through two fiber pairs, in which two fibers are cross-connected, as shown in Figure 1-3.

l          It is desired that the unidirectional links can be disconnected on being detected; and the ports shut down by DLDP can be restored after the fiber connections are corrected.

Applicable Product Matrix

Product series	Software version	Hardware version
S3610 series Ethernet switches	Release 5301 Release 5303	All versions
S5510 series Ethernet switches	Release 5301 Release 5303	All versions
S5500-EI series Ethernet switches	Release 2102	All versions
S7500E series Ethernet switches	Release 6300	All versions
S3500-EA series Ethernet switches	Release 5303	All versions

 

Configuration Procedure

1)        Configuration on Device A:

# Enable DLDP on GigabitEthernet 1/0/50 and GigabitEthernet 1/0/51.

<DeviceA> system-view

[DeviceA] interface gigabitethernet 1/0/50

[DeviceA-GigabitEthernet1/0/50] dldp enable

[DeviceA-GigabitEthernet1/0/50] quit

[DeviceA] interface gigabitethernet 1/0/51

[DeviceA-GigabitEthernet1/0/51] dldp enable

[DeviceA-GigabitEthernet1/0/51] quit

# Set the interval for sending Advertisement packets to 6 seconds.

[DeviceA] dldp interval 6

# Set the DelayDown timer to 2 seconds.

[DeviceA] dldp delaydown-timer 2

# Set the DLDP mode to enhanced mode.

[DeviceA] dldp work-mode enhance

# Set the port shutdown mode to auto mode.

[DeviceA] dldp unidirectional-shutdown auto

# Enable DLDP globally.

[DeviceA] dldp enable

# Display DLDP information.

[DeviceA] display dldp

 DLDP global status : enable

 DLDP interval : 6s

 DLDP work-mode : enhance

 DLDP authentication-mode  : none

 DLDP unidirectional-shutdown : auto

 DLDP delaydown-timer : 2s

 The number of enabled ports is 2.

 

Interface GigabitEthernet1/0/50

 DLDP port state : disable

 DLDP link state : down

 The neighbor number of the port is 0.

 

Interface GigabitEthernet1/0/51

 DLDP port state : disable

 DLDP link state : down

 The neighbor number of the port is 0.

The output information indicates that both GigabitEthernet1/0/50 and GigabitEthernet1/0/51 are in Disable state and the links are down, which means unidirectional links are detected and the two ports are thus shut down.

# Reset DLDP state for the ports shut down by DLDP.

[DeviceA] dldp reset

2)        Configuration on Device B:

The configuration on Device B is the same as that on Device A and is thus omitted.

 

 

Complete Configuration

l          Device A

#

 dldp enable

 dldp interval 6

 dldp work-mode enhance

 dldp delaydown-timer 2

#

interface GigabitEthernet1/0/50

 dldp enable

#

interface GigabitEthernet1/0/51

 dldp enable

l          Device B

The complete configuration on Device B is the same as that on Device A and is thus omitted.

Configuration Guidelines

1)        DLDP can detect unidirectional links only after all links are connected. Therefore, before enabling DLDP, make sure that optical fibers or copper twisted pairs are connected.

2)        DLDP takes effect only when it is enabled both globally and on a port.

3)        Set the interval for sending Advertisement packets to a value not longer than one-third of the STP convergence time. If the interval is too long, STP loops may occur before unidirectional links are torn down, and it takes a long time for the device to detect unidirectional links, thus causing more traffic forwarding errors; if the interval is too short, unnecessary Advertisement packets can be generated to consume bandwidth. Therefore, you are recommended to use the default value.

4)        To enable DLDP to operate properly, make sure the DLDP authentication modes and the passwords of the two sides of a link are the same.

5)        Destination MAC addresses of DLDP packets fall into two types: class A and class B, which is dependent on the software versions running on the device. To ensure that DLDP operates properly, interconnected devices must use destination MAC addresses of the same class. Table 1-1 describes the software versions using class-A destination MAC addresses (new addresses). The remaining versions use class-B destination MAC addresses.

Table 1-1 Software versions using class-A destination MAC addresses

Product series	Software versions
S3600 series Ethernet switches	Release 1510P06 and later
S5600 series Ethernet switches	Release 1510P06 and later
S5100 series Ethernet switches	Release 2200 and later
S3610 series Ethernet switches	All versions
S5510 series Ethernet switches	All versions
S5500-EI series Ethernet switches	All versions