R3303-HP 6600/HSR6600 Routers Interface Configuration Guide

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Figure 2 Single-port loopback
Figure 3 Multi-port loopback
You can enable loopback detection to detect loops on an interface and, if the interface supports the
loopback-detection action command, configure the protective action to take on the receiving interface
when a loop is detected, for example, to shut down the interface. Depending on whether a protective
action is configured, the device takes the actions in Table 1 to alle
viate the impact of the loop condition.
Table 1 Actions to take upon detection of a loop condition
Port type
Actions
No
p
rotective action is confi
g
ured A
p
rotective action is confi
g
ured
Access port
• Place the receiving interface in controlled
mode. The interface discards all incoming
packets, but still forwards outgoing packets.
• Generate traps.
• Delete all MAC address entries of the
interface.
• Perform the configured protective
action.
• Generate traps and log messages.
• Delete all MAC address entries of the
interface.
Hybrid or trunk
port
• Generate traps.
• If loopback detection control is enabled,
place the receiving interface in controlled
mode. The interface discards all incoming
packets, but still forwards outgoing packets.
• Delete all MAC address entries of the
interface.
• Create traps and log messages.
• If loopback detection control is
enabled, take the configured
protective action on the interface.
• Delete all MAC address entries of the
interface.
Configuration restrictions and guidelines
• To use loopback detection on an Ethernet interface, you must enable the function both globally and
on the interface.
• To disable loopback detection on all interfaces, run the undo loopback-detection enable command
in system view.