eBGP config and networks

[rhltechie]

Hi All,

I will be moving to a new mpls soon and wanted some input on my config. I am currently running eigrp inside my host network for all of my subnets. what is the best way to get my local networks into the ebgp config and out to the provider PE router? should I add them statically in the ebgp config or redistribute my eigrp into my ebgp?

TIA,

R

[tdrais]

The reasons I have heard to use the network statements rather than redistribution is that you avoid routing loops. I assume you will also redistribute the the EBGP that you receive from your other sites back into the EIGRP.

Also since you are typing in all the network statements you are in essence getting a output filter on your redistribution.

I would really like to hear from someone who knows why it would be preferable to redistribute the routes. I could see it being less a pain to configure but I would be filtering the redistribution so I would still have access lists were basically the same as keying in all the network statements

[kamlesh.sharma]

Hi R,

I think tdrais guru has answered your questione very well. i would like to add one more thing.

I will have all the routes belongs to MPLS backbone should be EIGRP 90 AD and all the routes which are coming from PE router should be D Ex 170 AD just to identify the routes in the routing table of all the router. Show if you want the routes otherthan your MPLS network to be published to customer site out from PE router than you have broad range of matching actions like tag and AD as well.

please rate if it helps.

Kamlesh

[rhltechie]

tdrias-

Maybe I am misunderstanding, but I did not get a clear answer out of this. are you saying that keying in the network statements into bgp is the best thing to do?

[tdrais]

We do it with network statements but many other people just redistribute it. I have only heard the arguments for doing it with the network statements. There is some limitation on how many network statements you can key in but its many more than the couple 100 networks statements I have put in a router. I was hoping someone else could indicate why you would do it with redistribution.

[rhltechie]

ah. I am leaning towards the use of the network statements. the only reason i am running bgp is to let the mpls network know if my host internet connection is down and therefore providing a backup internet connection in the cloud. i think i would prefer to leave my static statements as they are for everythign else.

[mheusinger]

Hello tdrais,

redistribution would allow you to insert routes into BGP based on certain features like tags. Those can also be used to avoid routing loops. Redistribution comes in handy, if you do not know the networks to be redistributed or it would create an unacceptable administrative burden. The latter usually is the case, when you have a MPLS L3VPN and a large customer. No FUN with typing network statements, if your customer is GE, Siemens, IBM, Microsoft, etc. and you are in charge of routing their internal routes. (You probably would need a pretty fast secretary for typing network statements ;-)

The situation with Internet is different, because RIPE and ARIN usually do not assign official IP addresses at rates faster than one can type network statements. ;-)

Stability is key for the Internet, convergence time is key for the MPLS L3VPN - both use BGP.

Hope this helps! Please rate all posts.

Regards, Martin

[tdrais]

Thanks martin.

I hate the keying of network statements and have been tring to find a argument to get a corporate standard changed. We have 20 class B nets chopped into lots and lots of pieces internally. I have a little script that takes a show ip route and generates the networks statements on the big sites.

Lucky this does not change much and in theory change management should prevent a change in the IGP we do not know about but everyone knows how change management really works.