loop-detection
Use this command to enable loop detection on the current LSR. This command detects looping LSPs, and prevent Label Request messages from looping because of non-merge capable LSRs. This loop detection mechanism is useful for networks of non time-to-live (non TTL) decrementing devices that can not allocate resources among traffic flows.
There are two methods supported for the loop detection mechanism: A Hop Count detection system, that is always enabled; and the Path Vector detection system, that can be toggled:
• Hop Count - During the setup of an LSP, the LSP passes a hop count with the LSP setup messages. This hop count is incremented by each node router participating in LSP establishment. If the hop count exceeds the maximum configured value, the LSP setup process is stopped, and a notification message is passed back to the message originator.
• Path Vector - A path vector contains a list of LSR identifiers. This is passed as a part of LSP setup messages. Each LSR participating in the LSP establishment adds its own LSR identifier to the path vector. If an LSR finds its own identifier in the path vector, it drops the message, and sends a message back to the originator.
The use of these messages ensures that a loop is detected while establishing a label switched path and before any data is passed over that LSP.
Use the no parameter to disable loop detection.
Command Syntax
loop-detection
no loop-detection
Parameters
None
Default
By default, loop detection is disabled
Command Mode
Router mode
Applicability
This command was introduced before OcNOS version 1.3.
Example
#configure terminal
(config)#router ldp
(config-router)#loop-detection
Last modified date: 10/17/2023