3Com Switch 8800 Configuration Guide
Chapter 36 MPLS Basic Capability Configuration
36-7
36.3.5 Configuring LDP Loop Detection Control
I. Enabling loop detection
It is used to enable or disable the loop detection function during LDP signaling process.
The loop detection includes maximum hop count mode and path vector mode.
The maximum hop count method refers to that the hop-count information is contained
in the message bound with the forwarding label, and the value pluses one for each hop.
When the value exceeds the threshold value, it is considered that a loop presents, and
the process for establishing LSP is terminated.
The path vector method refers to that the path information is recorded in the message
bound with the forwarding label, and, for every hop, the corresponding router checks if
its ID is contained in this record. If not, the router adds its ID into the record; and if yes,
it indicates that a loop presents and the process for establishing LSP is terminated.
When this method is used, if the defined maximum value is exceeded, it is considered
that a loop happens and the LSP establishment fails.
Perform the following configuration in the system view.
Table 36-12
Enable loop detection
Operation
Command
Enable loop detection
mpls ldp loop-detect
Disable loop detection
undo mpls ldp loop-detect
By default, the loop detection is disabled.
II. Setting the maximum hop count for loop detection
When maximum hop count mode is adopted for loop detection, the maximum
hop-count value can be defined. And if the maximum value is exceeded, it is
considered that a loop happens and the LSP establishment fails.
Perform the following configuration in the system view.
Table 36-13
Set the maximum hop count for loop detection
Operation
Command
Set maximum hop count for loop
detection
mpls ldp hops-count hop
-
number
Return to the default maximum hop
count
undo mpls ldp hops-count
The maximum hop count defaults to 32.
