Rip And Ripng; Graceful Restart And Mpls-Related Protocols; Ldp - Juniper EX9200 Features Manual

Chapter 10: Understanding How Graceful Restart Enables Uninterrupted Packet Forwarding When a Router Is Restarted

RIP and RIPng

Related
Documentation

Graceful Restart and MPLS-Related Protocols

LDP

Copyright © 2017, Juniper Networks, Inc.
When a router enabled for RIP graceful restart restarts, routes that have been configured
are protected. Because no helper router assists in the restart, these routes are retained
in the forwarding table while the router restarts (rather than being discarded or refreshed).
Graceful Restart Concepts on page 65
Graceful Restart System Requirements on page 73
Configuring Routing Protocols Graceful Restart on page 76
Verifying Graceful Restart Operation on page 220
Configuring Graceful Restart on page 87
Example: Configuring IS-IS for GRES with Graceful Restart on page 20
This section contains the following topics:
LDP on page 69
RSVP on page 70
CCC and TCC on page 70
LDP graceful restart enables a router whose LDP control plane is undergoing a restart to
continue to forward traffic while recovering its state from neighboring routers. It also
enables a router on which helper mode is enabled to assist a neighboring router that is
attempting to restart LDP.
During session initialization, a router advertises its ability to perform LDP graceful restart
or to take advantage of a neighbor performing LDP graceful restart by sending the graceful
restart TLV. This TLV contains two fields relevant to LDP graceful restart: the reconnect
time and the recovery time. The values of the reconnect and recovery times indicate the
graceful restart capabilities supported by the router.
The reconnect time is configured in Junos OS as 60 seconds and is not user-configurable.
The reconnect time is how long the helper router waits for the restarting router to establish
a connection. If the connection is not established within the reconnect interval, graceful
restart for the LDP session is terminated. The maximum reconnect time is 120 seconds
and is not user-configurable. The maximum reconnect time is the maximum value that
a helper router accepts from its restarting neighbor.
When a router discovers that a neighboring router is restarting, it waits until the end of
the recovery time before attempting to reconnect. The recovery time is the length of time
a router waits for LDP to restart gracefully. The recovery time period begins when an
initialization message is sent or received. This time period is also typically the length of
time that a neighboring router maintains its information about the restarting router, so
it can continue to forward traffic.
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