Cisco ASR 900 Series User Manual

CHAPTER 5
NSR LDP Support
The NSR LDP Support feature allows the Label Distribution Protocol (LDP) to continue to operate across
a Router Processor (RP) failure in redundant systems, without losing peer sessions. Before the introduction
of nonstop routing (NSR), LDP sessions with peers reset if an RP failover (in a redundant system) or a Cisco
In-Service Software Upgrade (ISSU) occurred. When peers reset, traffic is lost while the session is down.
Protocol reconvergence occurs after the session is reestablished.
When NSR is enabled, RP failover and Cisco ISSU events are not visible to the peer device, and the LDP
sessions that were established prior to failover do not flap. The protocol state learned from the peers persists
across an RP failover or Cisco ISSU event and does not need to be relearned.
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Finding Feature Information, page 99
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Prerequisites for NSR LDP Support, page 100
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Information About NSR LDP Support, page 100
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How to Configure NSR LDP Support, page 102
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Configuration Examples for NSR LDP Support, page 103
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Additional References for NSR LDP Support, page 105
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Feature Information for NSR LDP Support, page 105
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and
feature information, see Bug Search Tool and the release notes for your platform and software release. To
find information about the features documented in this module, and to see a list of the releases in which each
feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support.
To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)
99

Cisco ASR 900 Series Specifications

General

Brand	Cisco
Model	ASR 900 Series
Category	Network Router
Language	English