BGP and IGP

Unanswered Question
Jan 14th, 2010
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Hi All,


PFB my lab topology:


( CE1 ) -------------------------------(CE2)-----------(CE3) --------(CE4) -------------(CE5) ---------------------------------- (CE6)

BGP 64512                   BGP 64513            IGP - OSPF                 BGP64513                           BGP 64514
       
                                              |< ------------------------IBGP------------------------>|



I am simulating above lab wherein  CE2 to CE5 is an ISP running IGP : OSPF & iBGP on edge routers ( CE2 & CE5)
Do I need to redistribute my CORE ROUTES ( OSPF routes) into BGP and vice a versa for CE1\CE2 routes rechability ?

Or only BGP to IGP but then I am burdening my IGP ? Or IGP into BGP ..here I am exposing my core routes to CE1 & CE6( security issue).?


This is a normal internet type transport and not the MPLS.


Regards,
Santosh

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Giuseppe Larosa Thu, 01/14/2010 - 11:35
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Hello Santosh,


>> Or only BGP to IGP but then I am burdening my IGP ?


in a lab environment unless you are using an instrument to generate a lot of routes redistributing BGP into OSPF is possible without great worries.


OSPF can handlle few thousands of routes. So the question is how many routes are in BGP in your lab.


if CE3 doesn't speak BGP and no MPLS is involved (important note this)  BGP routes need to be redistributed into OSPF.

The same is true for CE4.


Hope to help

Giuseppe

santoshdpawar Thu, 01/14/2010 - 11:43
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Yes ... it works properly when I redistribute BGP to IGP.


I think I should use BGP full mesh instead of using IGP:OSPF for core connectivity provided my BGP knows all the CE's?

Giuseppe Larosa Thu, 01/14/2010 - 23:52
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Hello Santosh,

you can also make CE3 route-reflector server for CE2 and CE4 route reflector server for CE5.

And you need an iBGP session between CE3 and CE4.


you need to use neigh x.x.x.x route-reflector-client  on CE3, CE4 ( on the server side)


in this way you can see Route reflector in action that allows to solve iBGP scalability issues


if you use the iBGP full mesh or route reflectors you can remove redistribution of BGP into OSPF


Hope to help

Giuseppe

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