Loop detection commands -- display loopback-detection

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

mdc-admin

mdc-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 VLANs

GigabitEthernet1/0/3 None 10

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: ?span style='font:7.0pt "Times New Roman"'> Generates a log. ?span style='font:7.0pt "Times New Roman"'> Disables the port from learning MAC addresses. ?span style='font:7.0pt "Times New Roman"'> 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: ?span style='font:7.0pt "Times New Roman"'> Generates a log. ?span style='font:7.0pt "Times New Roman"'> 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).
VLANs | VLANs to which the interface belongs and where loops are detected.

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Loop detection commands -- loopback-detection action

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 or S-channel interface view:

loopback-detection action { block | no-learning | shutdown }

undo loopback-detection action

In Layer 2 aggregate interface view, S-channel aggregate interface view, or S-channel bundle 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

S-channel interface view

S-channel aggregate interface view

S-channel bundle interface view

Predefined user roles

network-admin

mdc-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 configuration applies to all ports. The per-port configuration applies to the individual ports. The per-port configuration takes precedence over the global configuration.

Example

# Set the loop protection action to shutdown on GigabitEthernet 1/0/1.

<Sysname> system-view

[Sysname] interface gigabitethernet 1/0/1

[System-GigabitEthernet1/0/1] loopback-detection action shutdown

Related commands

display loopback-detection

loopback-detection global action

Loop detection commands -- loopback-detection enable

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

S-channel interface view

S-channel aggregate interface view

S-channel bundle interface view

Predefined user roles

network-admin

mdc-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 no less than the ID for vlan-id1.

all: Specifies all existing VLANs.

Usage guidelines

To enable loop detection globally, use the loopback-detection global enable command.

The loop protection action on a port can be triggered even if loop detection is disabled on the port when the following requirements are met:

· Loop detection is enabled globally or on any other port on the device.

· The port receives a loop detection frame of any VLAN.

Example

# Enable loop detection on GigabitEthernet 1/0/1 for VLAN 10 through VLAN 20.

<Sysname> system-view

[Sysname] interface gigabitethernet 1/0/1

[System-GigabitEthernet1/0/1] loopback-detection enable vlan 10 to 20

Related commands

display loopback-detection

loopback-detection global enable

Loop detection commands -- loopback-detection global action

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

mdc-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 configuration applies to all ports. The per-port configuration applies to the individual ports. The per-port configuration takes precedence over the global configuration.

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

Loop detection commands -- loopback-detection global enable

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

mdc-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

To enable loop detection on a per-port basis, use the loopback-detection enable command in interface view.

The loop protection action on a port can be triggered even if loop detection is disabled on the port when the following requirements are met:

· Loop detection is enabled globally or on any other port on the device.

· The port receives a loop detection frame of any VLAN.

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

Loop detection commands -- loopback-detection interval-time

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

mdc-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