Cisco Systems 12.4 How to Configure MPLS LDP Graceful Restart

•mpls ldp graceful-restart timers neighbor-liveness
•mpls ldp graceful-restart timers max-recovery
How a Route Processor Advertises That It Supports MPLS LDP Graceful
Restart
A route processor that is configured to perform MPLS LDP GR includes the Fault Tolerant (FT) Type
Length Value (TLV) in the LDP initialization message. The route processor sends the LDP initialization
message to a neighbor to establish an LDP session.
The FT session TLV includes the following information:
• The Learn from Network (L) flag is set to 1, which indicates that the route processor is configured to
perform MPLS LDP GR.
• The Reconnect Timeout field shows the time (in milliseconds) that the neighbor should wait for a
reconnection if the LDP session is lost. In this release, the timer is set to 0, which indicates that if the
local router fails, its peers should not wait for it to recover. The timer setting indicates that the local
router is working in helper mode.
• The Recovery Time field shows the time (in milliseconds) that the neighbor should retain the MPLS
forwarding state during a recovery. If a neighbor did not preserve the MPLS forwarding state before
the restart of the control plane, the neighbor sets the recovery time to 0.
What Happens If a Route Processor Does Not Have LDP Graceful Restart
If two route processors establish an LDP session and one route processor is not configured for MPLS LDP
GR, the two route processors create a normal LDP session but do not have the ability to perform MPLS
LDP GR. Both route processors must be configured for MPLS LDP GR.
How to Configure MPLS LDP Graceful Restart
• Configuring MPLS LDP Graceful Restart, page 67
• Verifying the Configuration, page 69
Configuring MPLS LDP Graceful Restart
You must enable MPLS LDP GR on all route processors for an LDP session to be preserved during an
interruption in service.
MPLS LDP GR is enabled globally. When you enable MPLS LDP GR, it has no effect on existing LDP
sessions. New LDP sessions that are established can perform MPLS LDP GR.
How a Route Processor Advertises That It Supports MPLS LDP Graceful Restart
How to Configure MPLS LDP Graceful Restart
MPLS LDP Configuration Guide, Cisco IOS Release 12.4
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