4000 Router Series MPLS Command Reference

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.

<Sysname> system-view

[Sysname] mpls ldp

[Sysname-ldp] graceful-restart timer forwarding-hold 200

[Sysname-ldp] graceful-restart timer reconnect 100

Related commands

• display mpls ldp parameter

• graceful-restart