The MPLS-OPS Archive

[Umit.Inan@alcatel.com.tr]

Hello  ,

"Is it possible that all 10K routes (LSPs) make known to interior router
through lGP + label distribution protocol?"

Even the router,R2 in our example,can handle that amount of routes and
associated LSPs
from memory and cpu,switching hardware point of view.

As far as I'm concerned to distribute BGP learned routes into IGP would not
be an effective design.
As long as the interior routers support MPLS, they do not need receive any
of the BGP routes from the BGP speakers.
A default route information can be injected into R2's routing table with
the next hop information R3.
and R2 may bind a single label to all FECS.If I am not wrong this process
is known as Egress-Targeted Label Assignment.

Best Regards ,






Christopher Poh <tvpoh@essex.ac.uk> on 05/20/2002 02:59:53 PM
                                                              
                                                              
                                                              
  To:          Ajay Simha <asimha@cisco.com>                  
                                                              
  cc:          rajiva@cisco.com, Umit                         
               INAN/TR/ALCATEL@ALCATEL, raszuk@cisco.com,     
               mpls-ops@mplsrc.cm                             
                                                              
                                                              
                                                              
  Subject      Re: [MPLS-OPS]: AS Border Router               
  :                                                           
                                                              





Hi,

5/20/02 7:14:25 PM, Ajay Simha <asimha@cisco.com> wrote:

>On Mon, 20 May 2002, Christopher Poh wrote:
>
>>CP:Hi again,
>>CP:
>>CP:Thank you for clarifying about BGP peering. What about if an interior
>>CP:router (non-BGP peer) would want to establish a connection to exterior
>>CP:routes? Would the LSPs for those routes be available to the interior
>>CP:router?
>
>
>Via IGP? Would there be some label distribution protocol running between
this
>new non-BGP peer and the internal router? If so yes. If not no.

Is it possible that all 10K routes (LSPs) make known to interior router
through lGP + label distribution protocol?




                                                              
                                                              
                                                              
 To:       Rajiv Asati <rajiva@cisco.com>, Christopher Poh    
           <tvpoh@essex.ac.uk>                                
                                                              
 cc:       mpls-ops@mplsrc.com(bcc: Umit INAN/TR/ALCATEL)     
                                                              
                                                              
                                                              
 Subject:  Re: [MPLS-OPS]: AS Border Router                   
                                                              





Hello :

"So in the above topology, R3 may be learning 10,000 ipv4 routes from P1
(which is an eBGP neighbor) and may advertise those 10,000 ipv4 routes to
R1 and R4 (R3's iBGP neighbors). From R1 and R4 perspective, R3 is the
next-hop for all those 10,000 routes"

 RFC 1771 & 2858 states that when a BGP speaker advertises the route to an
internal peer, the
 advertising speaker should not modify the next hop information
associated with the route.

As far as I understand from this statement  for all routes learned from P1
next-hop should be P1 instead of R3
from R1 and R4 point of view,as long as next-hop self command is not
practiced at R3 .

Please let me know  if I am wrong.

Best Regards ,





Rajiv Asati <rajiva@cisco.com> on 05/20/2002 08:01:47 AM



  To:          Christopher Poh <tvpoh@essex.ac.uk>

  cc:          mpls-ops@mplsrc.com(bcc: Umit INAN/TR/ALCATEL)



  Subject      Re: [MPLS-OPS]: AS Border Router
  :






Christopher,

In a MPLS network, an ASBR, which is learning ipv4 routes via an eBGP
neighbor, typically doesn't allocate/advertise any label for those ipv4
routes that are advertised to its iBGP neighbors.

         <-------AS#1-------->        <-----AS#2.--->
         R1-------R2--------R3--------------P1---------------P2
                 |
                 R4

So in the above topology, R3 may be learning 10,000 ipv4 routes from P1
(which is an eBGP neighbor) and may advertise those 10,000 ipv4 routes to
R1 and R4 (R3's iBGP neighbors). From R1 and R4 perspective, R3 is the
next-hop for all those 10,000 routes. So, R1 will have a label to reach R3
and it will use that single label to reach all those 10,000 routes.
Similarly, R4 will also have a label to reach R3 and that label will also
be applied to any of those 10,000 prefixes.

As far as peering to all the internal routes are concerned, MPLS provides
the ability to make core routers BGP free. In other words, R2 above doesn't
need to be an iBGP neighbor and so it doesn't need to know about 10,000
prefixes.

Please let me know if I could be of more help.

Rajiv

At 09:13 PM 5/19/2002, Christopher Poh wrote:
>Hi,
>
>How does an AS border router advertise and make known to all other routers
>within a domain about label/FEC binding information for every exterior
>routes it
>carry? Does the router need to peer with all the interior routers in order
>to distribute this information?
>
>Hope someone could help me with this.
>
>
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