Configuring a Loop Detection Instance

Updated on 24 Jan 2024
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Loopbacks are frequently introduced in a network to assist with provisioning and troubleshooting. However, network loops can also have serious disruptive effects on the network including a loss of management connectivity. The loop detection feature is helpful when you must quickly identify the presence of loops at either the port or the tunnel level of the network.

If loop detection detects the presence of a loop on the network, the traffic flow on the incoming port affected by the loop can be blocked (i.e. squelched). You can configure the blocking functionality to block and/or unblock traffic automatically whenever a loop is detected, or you can block or unblock traffic manually. If a traffic block was in effect when a loop detection instance is disabled or deleted, the block is also cleared at the same time. In contrast, if you recreate or enable the loop detection instance at a later time, the traffic block is not automatically reapplied.

Use this page to manage loop detection instances, including the loop detection traffic block capability.

To set up a loop detection instance

Access the page Loop Detection ►Configuration ►Instances.
A summary of all loop detection instances that have been configured is displayed. The total number of instances found in the system is given in the lower-left corner of the page, as well as the index values of the items currently displayed on-screen (for example, [1–25] of 54). Use the page navigation links in the lower-right corner of the page to move between the pages of results.
Click Add to add a new loop detection instance, or click the Name of an existing loop detection instance to edit its settings.
Complete the required fields and click Add for a new loop detection instance or Apply for an existing loop detection instance.

For more information on specific parameters, refer to the following table.
Loop Detection Configuration (Loop Detection ►Configuration ►Instances)

Parameter	Description
Index	The unique identifier assigned to the loop detection instance once it has been created. You cannot modify this value. Note: The system supports up to 100 tunnel-level loop detection instances, in addition to one loop detection instance per port.
Type	Make a selection from the drop-down list to indicate the type of loop to detect. Acceptable values are: Link: Creates a loop detection instance on either a physical or a logical port. Tunnel: Creates a loop detection instance to poll an OLO for either untagged frames (no VLAN) or loops on a specific VLAN.
Resource	The name of the physical/logical port or interface polled by this loop detection instance is provided here.
Port	Make a selection from the drop-down list to select the physical port on which to listen for loops. The port assigned to a loop detection instance cannot be modified after you click Apply. A maximum of one loop detection instance can be created per port. Notes: Applies to link-level loop detection instances only. A loop detection instance can be created on physical and logical ports, but not on LAG ports. "Loop Detection" for other considerations related to the behavior of port-level loop detection instances.
Interface	Make a selection from the drop-down list to select the interface on which to poll for loops. UNI, ENNI and INNI interfaces are all supported; however, only the interfaces whose type is VLAN will appear in the drop-down list. Note: Applies to tunnel-level loop detection instances only.
Name	Enter a name to identify the loop detection instance. A maximum of 31 alphanumeric characters is supported. The name you enter can contain alphanumeric characters, spaces or special characters such as underscores and asterisks.
Enable	Select this box to activate this loop detection instance.
Interval(s)	Indicate the interval at which the loop detection instance will poll the specified resource for the presence of loops by sending a beacon, expressed in seconds. Minimum value: 1 (link level) or 2 (tunnel level) Maximum value: 30 Default value: Same as minimum value Note: In the summary screen, this value is displayed for your convenience; you cannot modify this value here.
State	Whether or not this loop detection instance is currently active is indicated here. To modify this value, you must open the loop detection instance directly.
Auto Block	Select this box to enable the auto-block mechanism. When the auto-block mechanism is enabled, traffic is automatically blocked within one second upon the detection of a loop on this port or tunnel.
Revertive	Select this box to enable revertive mode for the auto-block mechanism. When revertive mode is enabled, traffic is automatically unblocked within one second of a loop on this port or tunnel being resolved.

To delete a loop detection instance

Access the page Loop Detection ►Configuration ►Instances.
A summary of all loop detection instances that have been configured is listed in a grid.
For more information on specific parameters, refer to the table above.
Select the loop detection instance to delete from the list by clicking its Name.
The Loop Detection Configuration page opens, with the loop detection instance’s details displayed.
Click Delete.
The selected loop detection instance is permanently deleted; you are not prompted to confirm your actions. The system returns to the listing of loop detection instances on the previous page.

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Viewing Loop Detection Instance Details