Unanswered Question
Apr 23rd, 2009
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Currently we are running BGP loopbacks within our core and BGP on our MPLS network. EIGRP is used to converge the loopbacks within the core. I have been advised by a coworker that BGP should not be in the core and we should use EIGRP in the core and redistribute EIGRP(core) into BGP(mpls) and visa versa. Im on the fence and was wondering what others thought about the change.

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Jon Marshall Thu, 04/23/2009 - 06:00
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The answer is that it depends. BGP has a rich set of features to allow you ton influence traffic paths etc. but if you don't need any of these in the core then i would suggest simply using EIGRP. However there are some caveats to that -

1) Are the routes within the core easily summaisable. If so you may want to simply use network statements under your BGP config to advertise to the MPLS network rather than redistribute EIGRP into BGP.

2) I'm assuming the routes you receive from the MPLS network at the core site would be for other sites and perhaps a default for the Internet. If so redistributing BGP into EIGRP at each site is a reasonable thing to do.


Collin Clark Thu, 04/23/2009 - 06:27
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Adding to Jon's post-

We advertise the default route out to MPLS BGP from the head end. The remotes just get that route (all internet goes out our main site). At the remote sites we advertise the local networks. The edge networks only run BGP. Back at the head end we redistribute from BGP into EIGRP. This keeps things pretty clean at the remotes and it's easy to troubleshoot at both the remotes and the head end. Whether or not to run BGP in the core is dependent on your design. I would like to run BGP in our core, but our current design prevents from doing so. I would take a look at some of the SRND's for guidance.

DialerString_2 Thu, 04/23/2009 - 10:28
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Adding my 2 cents! My network is setup similar to Collin's. We are using BGP on the edge -also advertising the local networks- and EIGRP inside the core.

Like everyone has mentioned it's your design.

Giuseppe Larosa Sat, 04/25/2009 - 00:53
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Hello Kevin,

MPLS allows for doing what you do.

All service providers use an IGP to advertise network infrastructure and to build iBGP sessions.

Customer networks and service networks are advertised in BGP and thanks to recursion they are forwarded inside LSPs that have a destination = iBGP peer loopback address.

If you use MPLS in your infrastructure you could remove BGP from core routers with no need of redistribution of BGP into EIGRP.

if you are an enterprise using MPLS services of a provider to reach remote branch offices, you can take advantage of a routing architecture with EIGRP for infrastructure and BGP for services and remote branches with no need for redistribution (but you need iBGP to be everywhere, this is easily accomplished with BGP route reflectors).

It is better to propagate iBGP everywhere then redistributing BGP and EIGRP mutually.

Hope to help



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