Configuring LDP GR
Pre-configuration Tasks
LDP Graceful Restart (GR) ensures uninterrupted traffic transmission during a protocol restart or active/standby switchover because the forwarding plane is separated from the control plane.
Before configuring LDP GR, complete the following tasks:
Configure a local LDP session. For details, see Configuring Basic Functions of MPLS LDP.
Configure IGP GR. For details, see S2720, S5700, and S6700 V200R019C10 Configuration Guide - IP Unicast Routing.
Context
Table 1 describes timers used during LDP GR.
|
Timer |
Description |
Suggestion |
|---|---|---|
|
Reconnect timer |
After the GR Restarter performs an active/standby switchover, the GR Helper detects that the LDP session with the GR Restarter fails, and then starts the Reconnect timer and waits for reestablishment of the LDP session. The value of the Reconnect timer that takes effect on the GR Helper is the smaller one between the value of the Neighbor-liveness timer set on the GR Helper and the value of Reconnect timer set on the GR Restarter. |
When a network with a large number of routes is faulty, you can increase the value of the Reconnect timer to avoid that all the LDP sessions cannot recover within the default timeout period 300s. |
|
Recovery timer |
After the LDP session is reestablished, the GR Helper starts the Recovery timer and waits for the recovery of the LSP. The value of the Recovery timer that takes effect on the GR Helper is the smaller one between the value of the Recovery timer set on the GR Helper and the value of Recovery timer set on the GR Restarter. |
When a network with a large number of routes is faulty, you can increase the value of the Recovery timer to avoid that all the LSPs cannot recover within the default timeout period 300s. |
|
Neighbor-liveness timer |
The value of the neighbor-liveness timer defines the LDP GR period. The value of the Neighbor-liveness timer on the GR Restarter is the same as that of the Forwarding State Holding timer. |
When the number of LSPs on a network is small, you can set a smaller value for the Neighbor-liveness timer to shorten the GR period. |
Enabling or disabling LDP GR, or changing the LDP GR timer value cause LDP session reestablishment. To disable a device from re-establishing LDP sessions when LDP GR is enabled or disabled, or the LDP GR timer value is changed, run the no-renegotiate session-parameter-change graceful-restart command in the MPLS-LDP view.
Procedure
- Run system-view
The system view is displayed.
- Run mpls ldp
The MPLS LDP view is displayed.
- Run graceful-restart
The LDP GR function is enabled.
By default, the LDP GR function is disabled.
- (Optional) Run graceful-restart timer reconnect time
The Reconnect timer for the LDP session is set.
By default, the Reconnect timer is set to 300 seconds.
- (Optional) Run graceful-restart timer recovery time
The LSP Recovery timer is set.
By default, the LSP Recovery timer is set to 300 seconds.
- (Optional) Run graceful-restart timer neighbor-liveness time
The Neighbor-liveness timer is set.
By default, the Neighbor-liveness timer is 600 seconds.
Verifying the Configuration
Run the display mpls graceful-restart command to check information about GR of all protocols related to MPLS.
Run the display mpls ldp event gr-helper command to check GR Helper information.
Run the display mpls ldp [ all ] [ verbose ] command to check information about LDP.
Run the display mpls ldp session [ all ] [ verbose ] command to check information about the LDP session.