4000 Router Series Layer 2 - LAN Switching Configuration Guide

Loop detection configuration example

Network requirements

As shown in Figure 16, configure loop detection on Router A, so that Router A generates a log as a

notification and automatically shuts down the port on which a loop is detected.

Figure 16 Network diagram

Configuration procedure

1. Configure Router A:

# Create VLAN 100, and globally enable loop detection for the VLAN.

<RouterA> system-view

[RouterA] vlan 100

[RouterA–vlan100] quit

[RouterA] loopback-detection global enable vlan 100

# Configure Ethernet 2/1 and Ethernet 2/2 as trunk ports, and assign them to VLAN 100.

[RouterA] interface ethernet 2/1

[RouterA-Ethernet2/1] port link-type trunk

[RouterA-Ethernet2/1] port trunk permit vlan 100

[RouterA-Ethernet2/1] quit

[RouterA] interface ethernet 2/2

[RouterA-Ethernet2/2] port link-type trunk

[RouterA-Ethernet2/2] port trunk permit vlan 100

[RouterA-Ethernet2/2] quit

# Configure the global loop protection action as shutdown.

[RouterA] loopback-detection global action shutdown

# Set the loop detection interval to 35 seconds.

[RouterA] loopback-detection interval-time 35

Eth2/1

Router A

Router B Router C

Eth2/2

VLAN 100