08-Loop detection commands
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Use display loopback-detection to display the loop detection configuration and status.
Syntax
display loopback-detection
Views
Any view
Predefined user roles
network-admin
network-operator
context-admin
context-operator
Example
# Display the loop detection configuration and status.
<Sysname> display loopback-detection
Loopback detection is enabled.
Loopback detection interval is 30 second(s).
Loopback is detected on following interfaces:
Interface Action mode
GigabitEthernet1/0/3 None
Table 1 Command output
|
Field |
Description |
|
Action mode |
Loop protection action: · Block—When a loop is detected on a port, the device performs the following operations: ? Generates a log. ? Disables the port from learning MAC addresses. ? Blocks the port. · None—When a loop is detected on a port, the device generates a log but performs no action on the port. · No-learning—When a loop is detected on a port, the device generates a log and disables the port from learning MAC addresses. · Shutdown—When a loop is detected on a port, the device performs the following operations: ? Generates a log. ? Shuts down the port to disable the port from receiving or sending frames. The device automatically sets the port to the forwarding state after a time interval. Set the time interval by using the shutdown-interval command (see Fundamentals Command Reference). |
Use loopback-detection action to set the loop protection action on a per-port basis.
Use undo loopback-detection action to restore the default.
Syntax
In Layer 2 Ethernet interface view:
loopback-detection action { block | no-learning | shutdown }
undo loopback-detection action
In Layer 2 aggregate interface view:
loopback-detection action shutdown
undo loopback-detection action
Default
When the device detects a loop on a port, it generates a log but performs no action on the port.
Views
Layer 2 Ethernet interface view
Layer 2 aggregate interface view
Predefined user roles
network-admin
context-admin
Parameters
block: Enables the block mode. If a loop is detected, the device performs the following operations:
· Generates a log.
· Disables MAC address learning.
· Blocks the port.
Layer 2 aggregate interfaces do not support this keyword.
no-learning: Enables the no-learning mode. If a loop is detected, the device generates a log and disables MAC address learning on the port. Layer 2 aggregate interfaces do not support this keyword.
shutdown: Enables the shutdown mode. If a loop is detected, the device generates a log and shuts down the port. The device automatically sets the port to the forwarding state after the time interval set by using the shutdown-interval command (see Fundamentals Command Reference).
Usage guidelines
To set the loop protection action globally, use the loopback-detection global action command.
The global action applies to all ports. The per-port action applies to the individual ports. The per-port action takes precedence over the global action.
Example
# Set the loop protection action to shutdown on GigabitEthernet 1/2/5/1.
<Sysname> system-view
[Sysname] interface gigabitethernet 1/2/5/1
[System-GigabitEthernet1/2/5/1] loopback-detection action shutdown
display loopback-detection
loopback-detection global action
Use loopback-detection enable to enable loop detection on a per-port basis.
Use undo loopback-detection enable to disable loop detection on a port.
Syntax
loopback-detection enable vlan { vlan-id-list | all }
undo loopback-detection enable vlan { vlan-id-list | all }
Default
Loop detection is disabled on ports.
Views
Layer 2 Ethernet interface view
Layer 2 aggregate interface view
Predefined user roles
network-admin
context-admin
Parameters
vlan-id-list: Specifies a space-separated list of up to 10 VLAN items. Each item specifies a VLAN ID or a range of VLAN IDs in the form of vlan-id1 to vlan-id2. The value range for VLAN IDs is 1 to 4094. The ID for vlan-id2 must be equal to or greater than the ID for vlan-id1.
all: Specifies all existing VLANs.
Usage guidelines
You can enable loop detection globally or on a per-port basis. When a port receives a detection frame in any VLAN, the loop protection action is triggered on that port, regardless of whether loop detection is enabled on it.
Example
# Enable loop detection on GigabitEthernet 1/2/5/1 for VLAN 10 through VLAN 20.
<Sysname> system-view
[Sysname] interface gigabitethernet 1/2/5/1
[System-GigabitEthernet1/2/5/1] loopback-detection enable vlan 10 to 20
display loopback-detection
loopback-detection global enable
Use loopback-detection global action to set the global loop protection action.
Use undo loopback-detection global action to restore the default.
Syntax
loopback-detection global action shutdown
undo loopback-detection global action
Default
When the device detects a loop on a port, it generates a log but performs no action on the port.
Views
System view
Predefined user roles
network-admin
context-admin
Parameters
shutdown: Enables the shutdown mode. If a loop is detected, the device generates a log and shuts down the port. The device automatically sets the port to the forwarding state after you set the time interval by using the shutdown-interval command (see Fundamentals Command Reference).
Usage guidelines
To set the loop protection action on a per-port basis, use the loopback-detection action command in interface view.
The global action applies to all ports. The per-port action applies to the individual ports. The per-port action takes precedence over the global action.
Example
# Set the global loop protection action to shutdown.
<Sysname> system-view
[System] loopback-detection global action shutdown
Related commands
display loopback-detection
loopback-detection action
Use loopback-detection global enable to enable loop detection globally.
Use undo loopback-detection global enable to disable loop detection globally.
Syntax
loopback-detection global enable vlan { vlan-id-list | all }
undo loopback-detection global enable vlan { vlan-id-list | all }
Default
Loop detection is globally disabled.
Views
System view
Predefined user roles
network-admin
context-admin
Parameters
vlan-id-list: Specifies a space-separated list of up to 10 VLAN items. Each item specifies a VLAN ID or a range of VLAN IDs in the form of vlan-id1 to vlan-id2. The value range for VLAN IDs is 1 to 4094. The ID for vlan-id2 must be equal to or greater than the ID for vlan-id1.
all: Specifies all existing VLANs.
Usage guidelines
You can enable loop detection globally or on a per-port basis. When a port receives a detection frame in any VLAN, the loop protection action is triggered on that port, regardless of whether loop detection is enabled on it.
Example
# Globally enable loop detection for VLAN 10 through VLAN 20.
<Sysname> system-view
[System] loopback-detection global enable vlan 10 to 20
Related commands
display loopback-detection
loopback-detection enable
Use loopback-detection interval-time to set the loop detection interval.
Use undo loopback-detection interval-time to restore the default.
Syntax
loopback-detection interval-time interval
undo loopback-detection interval-time
Default
The loop detection interval is 30 seconds.
Views
System view
Predefined user roles
network-admin
context-admin
Parameters
interval: Sets the loop detection interval in the range of 1 to 300 seconds.
Usage guidelines
With loop detection enabled, the device sends loop detection frames at the specified interval. A shorter interval offers more sensitive detection but consumes more resources. Consider the system performance and loop detection speed when you set the loop detection interval.
Example
# Set the loop detection interval to 10 seconds.
<Sysname> system-view
[Sysname] loopback-detection interval-time 10
Related commands
display loopback-detection
