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I'm a sys admin by trade but I've been tasked with heading up a team that will be implementing OSPF between the different offices in our company. I don't have any experience with OSPF so I'm not sure what all needs to be done to bring this project to completion.

Can somebody with OSPF experience please provide me with some sort of outline of what questions need to be answered and what needs to be setup to get OSPF in place? I'm not really looking for the deep technical aspects of this, more the high level management items that needs to be looked at and assigned to different parties.

Currently we have a link setup between offices A and B but we need to setup an alternate path passing through offices C, D, or E to setup an alternate route to get from A to B.

Thanks in advance...if there is a site that this would be better addressed to, please feel free to let me know.

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2 Answers 2

up vote 3 down vote accepted

I think this is within your grasp, but you'll need to go slowly.

What you're trying to accomplish here is to have each of your routing devices inject networks that they are either statically routed to or directly connected to into a routing table and then advertise it to adjacent peers. Static routes are usually preferred so you should be able to experiment with this without messing with your existing setup.

HOW you go about doing this requires more information. What kinds of devices interconnect the sites (Cisco/Juniper/etc.)? Are they point to point connections, VPN?

One could implement OSPF without knowing all of the mechanics ahead of time, but it will help.

Check out: http://en.wikipedia.org/wiki/Open_Shortest_Path_First

and: http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml

Read slowly, ingest.

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This is a great start, thanks for pointing me in the right direction. This should really help me begin to ask the questions that will be important in setting up a roadmap to completion for this project. –  Luniz Nov 9 '10 at 15:12

There are a couple of things to consider up-front.

OSPF uses a concept of "areas". Area 0 is "the backbone" and should ideally touch all routers that provide inter-site connectivity, since it's much (MUCH) easier to implement OSPF if you have "a backbone". Second, you need to decide if you should split your sites into individual areas or not. This primarily depends on how pure a design you want and how many nodes you have in the network. It may also depend on how your current IP allocation is made (and to what extent you're happy renumbering parts or all of your network).

After that, consider if you will be wanting to use default metrics (essentially an inverse of the line-speed) or if you want to use custom metrics. This would primarily depend on how fast your links are. If you're on "100 Mbps or less" and don't need to cater to any split-backbone design (a previous network I managed had two cores, one for national/peering-point traffic and one for traffic through Tier-1 ISPs, running a coherent OSPF across the whole, using custom metrics to separate the national and "international" traffic).

At some point, probably towards the end of the design, you also need to decide if you're going to be using custom timers or if default timers are OK. This makes a difference for reconvergence times (essentially, how fast the network reacts to changes, like links dropping or coming back).

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