The configuration for LDP IGP synchronization resides in respective IGPs (OSPF and IS-IS) and there
is no LDP-specific configuration for enabling of this feature. However, there is a specific LDP configuration
for IGP sync delay timer.
Note
Related Topics
Configuring LDP IGP Synchronization: OSPF, on page 50
Configuring LDP IGP Synchronization—OSPF: Example, on page 83
Configuring LDP IGP Synchronization: ISIS, on page 55
Configuring LDP IGP Synchronization—ISIS: Example, on page 83
Configuring LDP IGP Synchronization Delay Interval, on page 56
IGP Auto-configuration
To enable LDP on a large number of interfaces, IGP auto-configuration lets you automatically configure LDP
on all interfaces associated with a specified IGP interface; for example, when LDP is used for transport in the
core network. However, there needs to be one IGP set up to enable LDP auto-configuration.
Typically, LDP assigns and advertises labels for IGP routes and must often be enabled on all active interfaces
by an IGP. Without IGP auto-configuration, you must define the set of interfaces under LDP, a procedure
that is time-intensive and error-prone.
LDP auto-configuration is supported for IPv4 unicast family in the default VRF. The IGP is responsible
for verifying and applying the configuration.
Note
You can also disable auto-configuration on a per-interface basis. This permits LDP to enable all IGP interfaces
except those that are explicitly disabled and prevents LDP from enabling an interface when LDP
auto-configuration is configured under IGP.
Related Topics
Enabling LDP Auto-Configuration for a Specified OSPF Instance, on page 59
Enabling LDP Auto-Configuration in an Area for a Specified OSPF Instance, on page 61
Disabling LDP Auto-Configuration, on page 62
Configuring LDP Auto-Configuration: Example, on page 84
IGP Synchronization Process Restart Delay
In the LDP IGP synchronization process, failures and restarts bear a heavy stress on the network. Multiple
IGP synchronization notifications from LDP to IGP, and potential generation of multiple SPF and LSAs are
known to effect the CPU load considerably. This results in considerable traffic loss when the LDP process
fails.
The LDP IGP Synchronization Process Restart Delay is a feature that enables a process-level delay for
synchronization events when the LDP fails or restarts. This delay defers the sending of sync-up events to the
IGP until most or all the LDP sessions converge and also allows the LDP to stabilize. This allows the LDP
Cisco IOS XR MPLS Configuration Guide for the Cisco CRS Router, Release 5.1.x
18
Implementing MPLS Label Distribution Protocol
IGP Auto-configuration
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