[j-nsp] Difference between "ldp egress-policy" and "ldp export|import"

Mark Tinka mtinka at globaltransit.net
Thu May 14 15:31:21 EDT 2009

On Friday 15 May 2009 02:40:24 am Thiago Drechsel wrote:

> A quick question: What's the difference between "ldp
> egress-policy"...

This one tells the router to determine which prefixes should 
be announced into LDP.

With this command unconfigured, only the Loopback address is 
announced into LDP. If you would like to announce other 
prefixes, e.g., static routes, direct routes, e.t.c., you 
would use this feature to do so.

Note: your egress policy list should contain your Loopback
      address; if it doesn't, your Loopback address won't be
      announced into LDP anymore.

> and "ldp export...

This one tells the router to determine which label bindings 
to announce to its LDP neighbors. These labels represent 
prefixes, i.e., label bindings (to prefixes).

For instance, if label 20000 is bound to prefix and label 30000 is bound to prefix, you can setup an export filter that blocks from being announced. This will cause the 
router not to announce label 30000, but still announce label 

Note: even though you may be able to prevent some bindings
      from being announced to the router's LDP neighbors,
      those same bindings can still be used by the local
      router as a valid LSP.

> |import".

This works in the reverse of 'export', as above. 

Note: the difference with the 'export' feature is that you
      would still see the label binding for the prefixes
      that have been filtered, in LDP; however, the router
      will not consider said binding as a usable LSP.

Hope this helps.


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