32
Step Command
Remarks
b. vpn-instance
vpn-instance-name
3.
Configure an IPv4 label
acceptance policy.
accept-label peer
peer-lsr-id
prefix-list
prefix-list-name
By default, LDP accepts all IPv4
FEC-label mappings.
4.
Configure an IPv6 label
acceptance policy.
ipv6 accept-label peer
peer-lsr-id
prefix-list
prefix-list-name
By default, LDP accepts all IPv6
FEC-label mappings.
43B
Configuring LDP loop detection
LDP detects and terminates LSP loops in the following ways:
•
Maximum hop count
—LDP adds a hop count in a label request or label mapping message.
The hop count value increments by 1 on each LSR. When the maximum hop count is reached,
LDP considers that a loop has occurred and terminates the establishment of the LSP.
•
Path
vector
—LDP adds LSR ID information in a label request or label mapping message. Each
LSR checks whether its LSR ID is contained in the message. If it is not, the LSR adds its own
LSR ID into the message. If it is, the LSR considers that a loop has occurred and terminates
LSP establishment. In addition, when the number of LSR IDs in the message reaches the path
vector limit, LDP also considers that a loop has occurred and terminates LSP establishment.
To configure LDP loop detection:
Step Command Remarks
1.
Enter system view.
system-view
N/A
2.
Enter LDP view or enter
LDP-VPN instance view.
•
Enter LDP view:
mpls ldp
•
Enter LDP-VPN instance view:
a. mpls ldp
b. vpn-instance
vpn-instance-name
N/A
3.
Enable loop detection.
loop-detect
By default, loop detection is
disabled.
After loop detection is
enabled, the device uses both
the maximum hop count and
the path vector methods to
detect loops.
4.
Set the maximum hop
count.
maxhops
hop-number
By default, the maximum hop
count is 32.
5.
Set the path vector limit.
pv-limit
pv-number
By default, the path vector
limit is 32.
NOTE:
The LDP loop detection feature is applicable only in networks comprised of devices that do not
support TTL mechanism, such as ATM switches. Do not use LDP loop detection on other networks
because it only results in extra LDP overhead.