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Category: OSPF

Generating OSPF, BGP and MPLS/VPN Configurations from Network Data Model

Over a month ago I decided to create a lab network to figure out how to solve an interesting Inter-AS MPLS/VPN routing challenge. Instead of configuring half a dozen routers I decided to develop a fully-automated deployment because it will make my life easier.

I finally got to a point where OSPF, LDP, BGP (IPv4 and VPNv4) and MPLS/VPN configurations are created, deployed and verified automatically.

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Why Would I Use BGP and not OSPF between Servers and the Network?

While we were preparing for the Cumulus Networks’ Routing on Hosts webinar Dinesh Dutt sent me a message along these lines:

You categorically reject the use of OSPF, but we have a couple of customers using it quite happily. I'm sure you have good reasons and the reasons you list [in the presentation] are ones I agree with. OTOH, why not use totally stubby areas with the hosts being in such an area?

How about:

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Do We Still Need OSPF Areas and Summarization?

One of my ExpertExpress design discussions focused on WAN network design and the need for OSPF areas and summarization (the customer had random addressing and the engineers wondered whether it makes sense to renumber the network to get better summarization).

I was struggling with the question of whether we still need OSPF areas and summarization in 2016 for a long time. Here are my thoughts on the topic; please share yours in the comments.

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BGP or OSPF? Does Topology Visibility Matter?

One of the comments added to my Using BGP in Data Centers blog post said:

With symmetric fabric… does it make sense for a node to know every bit of fabric info or is reachability information sufficient?

Let’s ignore for the moment that large non-redundant layer-3 fabrics where BGP-in-Data-Center movement started don’t need more than endpoint reachability information, and focus on a bigger issue: is knowledge of network topology (as provided by OSPF and not by BGP) beneficial?

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Combining DMVPN with Existing MPLS/VPN Network

One of the Expert Express sessions focused on an MPLS/VPN-based WAN network using OSPF as the routing protocol. The customer wanted to add DMVPN-based backup links and planned to retain OSPF as the routing protocol. Not surprisingly, the initial design had all sorts of unexpectedly complex kludges (see the case study for more details).

Having a really smart engineer on the other end of the WebEx call, I had to ask a single question: “Why don’t you use BGP everywhere” and after a short pause got back the expected reply “wow ... now it all makes sense.”

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