Overview Of Label Distribution Protocol; Configuring Label Distribution Protocol - Cisco NCS 5500 Series Configuration Manual
Mpls ios xr release 6.2.x
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Overview of Label Distribution Protocol
• We recommend to use a lower session holdtime bandwidth such as neighbors so that a session down
Overview of Label Distribution Protocol
In IP forwarding, when a packet arrives at a router the router looks at the destination address in the IP header,
performs a route lookup, and then forwards the packet to the next hop. MPLS is a forwarding mechanism in
which packets are forwarded based on labels. Label Distribution Protocols assign, distribute, and install the
labels in an MPLS environment. It is the set of procedures and messages by which Label Switched Routers
(LSRs) establish LSPs through a network by mapping network-layer routing information directly to data-link
layer switched paths. These LSPs may have an endpoint at a directly attached neighbor (comparable to IP
hop-by-hop forwarding), or may have an endpoint at a network egress node, enabling switching via all
intermediary nodes.
LSPs can be created statically, by RSVP traffic engineering (TE), or by LDP. LSPs created by LDP perform
hop-by-hop path setup instead of an end-to-end path. LDP enables LSRs to discover their potential peer routers
and to establish LDP sessions with those peers to exchange label binding information. Once label bindings
are learned, the LDP is ready to setup the MPLS forwarding plane.
For more information about setting up LSPs, see
Configuring Label Distribution Protocol
Depending on the requirements, LDP requires some basic configuration tasks described in the following
topics:
Configuring Label Distribution Protocol
This section explains the basic LDP configuration. LDP should be enabled on all interfaces that connects the
router to potential LDP peer routers. You can enable LDP on an interface by specifying the interface under
mpls ldp configuration mode.
Configuration Example
This example shows how to enable LDP over an interface.
RP/0/RP0/CPU0:Router(config)#
RP/0/RP0/CPU0:Router(config-ldp)#
RP/0/RP0/CPU0:Router(config-ldp)#
RP/0/RP0/CPU0:Router(config-ldp-if)#
MPLS Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
4
occurs before an adjacency-down on a neighbor. Therefore, the following default values for the hello
times are listed:
• Holdtime is 15 seconds.
• Interval is 5 seconds.
For example, the LDP session holdtime can be configured as 30 seconds by using the holdtime command.
MPLS Label Distribution Protocol : Details, on page
mpls ldp
router-id 192.168.70.1
interface HundredGigE 0/0/0/5
commit
Implementing MPLS Label Distribution Protocol
11.
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