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Re: Re: IGP-LDP interaction

  • From: <richard.james@rogers.com>
  • Date: Thu, 22 Jan 2004 9:18:28 -0500
  • CC: <mpls-ops@mplsrc.com>
  • Resent-Date: Thu, 22 Jan 2004 09:52:26 -0500
  • To: Eric Osborne <eosborne@cisco.com>, Harpreet Singh <harpreet_singh_2000@yahoo.com>
  • X-Authentication-Info: Submitted using SMTP AUTH LOGIN at fep01-mail.bloor.is.net.cable.rogers.com from [127.0.0.1] using ID <richard.james@rogers.com> at Thu, 22 Jan 2004 09:18:28 -0500

In order to advertise a label received for a particular prefix, a router has to have a route in its IGP that is an *exact* match for the prefix.

Here's a question: if a router has a route that is less specific than the prefix in the LDP mapping, but still matches, could it advertise the LDP mapping in that case? So basically doing a longest match instead of an exact match? I understand that most routers need the exact match today, is this because of implementation or is it the standard dictating it?

> 
> From: Eric Osborne <eosborne@cisco.com>
> Date: 2004/01/22 Thu AM 07:05:19 EST
> To: Harpreet Singh <harpreet_singh_2000@yahoo.com>
> CC: mpls-ops@mplsrc.com
> Subject: Re: [MPLS-OPS]: IGP-LDP interaction
> 
> On Thu, Jan 22, 2004 at 02:32:15AM -0800, Harpreet Singh wrote:
> > 
> > Can anyone tell me/ refer me to some good pointers on
> > how OSPF interacts with LDP? 
> 
> They don't really interact, they're two different protocols.
> 
> > Specifically in JUNOS, the rouyter does not distribute labels to its
> > LDP neighbors for prefixes that it odes not have in its IGP although
> > it recieved a downstream label for it from another neighbor. Is
> > there some standard for this?
> 
> IOS works the same way.  The idea with LDP (in non-Martini mode,
> anyways) is that it distributes labels for routes it has in its IGP
> routing table.  LDP is not a routing protocol, and does not give out
> reachability information that routing does not also give out.
> 
> 
> 
> eric
> 
> > 
> > Thanks in advance.
> > HS


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