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LDP Configuration Commands
Generic Commands
ldp
Syntax
[no] ldp
Context
config>router
Default
This command creates the context to configure an LDP parameters. LDP is not enabled by default and
must be explicitely enabled (no shutdown).
To suspend the LDP protocol, use the shutdown command. Configuration parameters are not
affected.
The no form of the command deletes the LDP protocol instance, removing all associated
configuration parameters. The LDP instance must first be disabled with the shutdown command
before being deleted.
Default
none (LDP must be explicitly enabled)
ldp-shortcut
Syntax
[no] ldp-shortcut
Context
config>router
Description
This command enables the resolution of IGP routes using LDP LSP across all network interfaces
participating in the IS-IS and OSPF routing protocol in the system.
When LDP shortcut is enabled, LDP populates the routing table with next-hop entries corresponding
to all prefixes for which it activated an LDP FEC. For a given prefix, two route entries are populated
in the system routing table. One corresponds to the LDP shortcut next-hop and has an owner of LDP.
The other one is the regular IP next-hop. The LDP shortcut next-hop always has preference over the
regular IP next-hop for forwarding user packets and specified control packets over a given outgoing
interface to the route next-hop.
All user and specified control packets for which the longest prefix match in RTM yields the FEC
prefix will be forwarded over the LDP LSP.
When an IPv4 packet is received on an ingress network interface, or a regular IES interface, the
lookup of the packet by the ingress forwarding engine will result in the packet being sent labeled with
the label stack corresponding to the NHLFE of the LDP LSP when the preferred RTM entry
corresponds to an LDP shortcut.
If the preferred RTM entry corresponds to an IP next-hop, the IPv4 packet is forwarded unlabelled.
When ECMP is enabled and multiple equal-cost next-hops exit for the IGP route, the ingress
forwarding engine will spray the packets for this route based on hashing routine currently supported
7950 SR OS MPLS Configuration Guide
LDP Configuration Commands
Page 397
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