Cisco Cisco IOS Software Release 12.4(3)

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12.0(22)S

This feature was integrated into Cisco IOS Release 12.0(22)S. The mpls 
ldp neighbor targeted-session command and the interface keyword for 
the mpls ldp advertise-labels command were added.

12.0(23)S

This feature was integrated into Cisco IOS Release 12.0(23)S. Default 
values for the mpls ldp discovery command holdtime and interval 
keywords were changed.

12.2(13)T

This feature was integrated into Cisco IOS Release 12.2(13)T.

12.4(3)

The default MPLS label distribution protocol changed from TDP to LDP. 
If no protocol is explicitly configured by the mpls label protocol 
command, LDP is the default label distribution protocol. See the mpls 
label protocol (global configuration) command for more information. 

Use caution when upgrading the image on a router that uses TDP. 
Ensure that the TDP sessions are established when the new image 
is loaded. You can accomplish this by issuing the global 
configuration command mpls label protocol tdp. Issue this 
command and save it to the startup configuration before loading 
the new image. Alternatively, you can enter the command and save 
the running configuration immediately after loading the new 
image. 

LDP configuration commands are saved by using the MPLS form of the 
command rather than the tag-switching form. Previously, commands were 
saved by using the tag-switching form of the command, for backward 
compatibility. See the 

 for more information. 

12.4(5)

The vrf vrf-name keyword/argument pair was added for the mpls ldp 
router-id command to allow you to associate the LDP router ID with a 
nondefault VRF.