H3C Technologies H3C S7500E Series Switches - Manual (Page 61)

2-19
To do… Use the command… Remarks
Specify the label distribution
control mode
label-distribution { independent |
ordered }
Optional
Ordered by default
For LDP sessions existing before
the command is configured, you
need to reset the LDP sessions for
the specified label distribution
control mode to take effect.
Enable label re-advertisement for
DU mode
du-readvertise
Optional
Enabled by default
Set the interval for label
re-advertisement in DU mode
du-readvertise timer value
Optional
30 seconds by default
Configuring LDP Loop Detection
LSPs established in an MPLS domain may be looping. The LDP loop detection mechanism can detect
looping LSPs and prevent LDP messages from looping forever.
LDP loop detection can be in either of the following two modes:
Maximum hop count
A label request message or label mapping message carries information about its hop count, which
increments by 1 for each hop. When this value reaches the specified limit, LDP considers that a loop is
present and terminates the establishment of the LSP.
Path vector
A label request message or label mapping message carries path information in the form of path vector
list. When such a message reaches an LSR, the LSR checks the path vector list of the message to
see whether its MPLS LSR ID is in the list. If not, the LSR will add its LSR ID to the path vector list; if
yes, the LSR considers that a loop appears and terminates the establishment of the LSP.
In the path vector mode, you also need to specify the maximum number of hops of an LSP. An LSR
will also terminate the establishment of an LSP when the hop count of the path, or the length of the
path vector, reaches the specified limit.
Follow these steps to configure LDP loop detection:
To do… Use the command… Remarks
Enter system view system-view —
Enter MPLS LDP view mpls ldp —
Enable loop detection loop-detect
Required
Disabled by default