R21xx-HP FlexFabric 11900 MPLS Command Reference

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Syntax
graceful-restart timer { forwarding-hold hold-time | reconnect reconnect-time }
undo graceful-restart timer { forwarding-hold | reconnect }
Default
The MPLS Forwarding State Holding timer is 180 seconds and the Reconnect timer is 120 seconds.
Views
LDP view
Predefined user roles
network-admin
Parameters
forwarding-hold hold-time: Specifies the MPLS Forwarding State Holding time in the range of 60 to 600
seconds. This time specifies how long the local LSR retains its MPLS forwarding entries after the control
plane of the local LSR restarts.
reconnect timeout: Specifies the Reconnect time in the range of 60 to 300 seconds. This time specifies the
period the local LSR expects the peer to wait for LDP session re-establishment after the peer detects an
LDP session failure. The local LSR sends the Reconnect time to the peer.
Usage guidelines
The MPLS Forwarding State Holding time must be greater than the Reconnect time.
In a GR process, the timers work as follows:
1. When LDP restarts, the GR restarter starts the MPLS Forwarding State Holding timer, and marks the
MPLS forwarding entries as stale. When a GR helper detects that the LDP session with the GR
restarter is down, it marks the FEC-label mappings learned from the session as stale and starts the
Reconnect timer, the value of which is received from the GR restarter.
2. After the LDP restart, the GR restarter re-establishes an LDP session with the GR helper. If the LDP
session is not set up before the Reconnect timer expires, the GR helper deletes stale FEC-label
mappings and corresponding MPLS forwarding entries. If the LDP session is successfully set up
before the Reconnect timer expires, the GR restarter sends the remaining time of the MPLS
Forwarding State Holding timer as the LDP Recovery time to the GR helper.
3. After the LDP session is re-established, the GR helper starts the LDP Recovery timer.
4. The GR restarter and the GR helper exchange label mappings and update their MPLS forwarding
tables.
The GR restarter compares each received label mapping against stale MPLS forwarding entries. If
a match is found, the restarter deletes the stale mark for the matching entry. Otherwise, it adds a
new entry for the label mapping.
The GR helper compares each received label mapping against stale FEC-label mappings. If a
match is found, the helper deletes the stale mark for the matching mapping. Otherwise, it adds the
received FEC-label mapping and a new MPLS forwarding entry for the mapping.
5. When the MPLS Forwarding State Holding timer expires, the GR restarter deletes all stale MPLS
forwarding entries.
6. When the LDP Recovery timer expires, the GR helper deletes all stale FEC-label mappings.
Examples
# Set the MPLS Forwarding State Holding time to 200 seconds, and the Reconnect time to 100 seconds.