IGP for IP/MPLS based enterprise network

Answered Question
Nov 15th, 2007
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Hi,

in light of the trend to migrate the enterprise WAN from layer-2 based circuits to layer-3 MPLS VPN. Is there a

need to match such change when designing WAN routing. As example, in a WAN of 1,000 router, we mostly used to consider OSPF with some area xs for the regions and then summerize the routes advertized into each area. This is not the case in IP/MPLS based WAN, since it is

any-to-any technology, and all the routes for the same VRF will show up in every router.


I just wonder if any one is aware of a URL talk about selecting the IGP for IP/MPLS based enterprise network.

Thanks


Sami


Correct Answer by Joseph W. Doherty about 9 years 7 months ago

I think so. What you can structure is a WAN that becomes your own private Internet. Each site routes within it however you chose but communcates its address block using eBGP to the WAN. (Somewhat similar to doing the same on the Internet if you eBGP peer with your ISP and pass route information both ways.)

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Joseph W. Doherty Thu, 11/15/2007 - 12:58
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If you really intend to extend MPLS across you LAN/WAN, you might be somewhat restricted in selection of an IGP.


If you mean you'll be using a provider MPLS L3 VPN WAN, then what often works well is BGP between the CE and PE routers where your CE advertises a single address block for the site. Within the site, you can use whatever IGP you want.

ccie16351 Thu, 11/15/2007 - 14:10
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Hi,

I mean I will be using provider MPLS L3 VPN, and I will be using eBGP between my 1000+ CEs to the nearest PE. The enterprise network is Hub and Spoke, Two hubs; the Primary Data Center and DRC.


I wounder if I still do need an IGP to peer between my CEs ?.

Joseph W. Doherty Thu, 11/15/2007 - 17:05
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"I wounder if I still do need an IGP to peer between my CEs ?. " If you mean across the WAN, no. BGP should cover it.

ccie16351 Thu, 11/15/2007 - 22:50
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then the answer to my equerry is Enterprise WAN built on IP/MPLS no longer need an IGP !!



Correct Answer
Joseph W. Doherty Fri, 11/16/2007 - 04:15
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I think so. What you can structure is a WAN that becomes your own private Internet. Each site routes within it however you chose but communcates its address block using eBGP to the WAN. (Somewhat similar to doing the same on the Internet if you eBGP peer with your ISP and pass route information both ways.)

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