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Webcast-Catalyst9k
New Member

OSPF within FR hub and spoke

We have a network which is being deployed in a hub and spoke architecture using frame relay for the most part. All sites comes back to the main HQ routers (there are two for redundancy and fault tolerance).

We are thinking of deploying OSPF within this network but to do this we either have one large area 0 (not what I want at all) or we have 75 areas (stubs) with one router in them.

Would it be better for us to consider another solution? As stated, there 75 sites, all Cisco routers ranging from 1700, 2600's and 3660's.

Thanks for your input.

4 REPLIES
New Member

Re: OSPF within FR hub and spoke

Hi,

You have two reasonable choices for Your routing protocol:

OSPF, EIGRP

For ospf, there will be quite a complex configuration - network type under interface, DR, BDR, virtual-links, stub areas etc, also, if You going to use 1600 series You will need IP PLUS IOS set. You can use area 0 on Your main LAN, stub area 1 on Your Hub and Spoke FrameRelay, and then either assign different areas to Your LAN connections or NSSA on Hub and Spoke and redistribute connected, in both cases You will need virtual links.

If using single ospf area, it will work the same well, but You will have "messed-up" routing table.

You can use EIGRP, if all Your routers are Cisco - it would ease up Your routing protocol configuration and finetune it afterwards with distribute lists and/or sumary-addresses or auto-summary and it is supported on all Cisco routers.

In general, many protocols will be fine in Your scenario, but I would use EIGRP and inbound distribute-list allowing only the default route into spoke routers - like this

router eigrp 100

net x.x.x.x

net y.y.y.y

distribute-list 1 in ser0

access-list 1 permit 0.0.0.0

As You can see, quick and simple, and it works OK.

But it is Your decision which way You want to go.

Should You decide to go with OSPF contact me directly and I will help You designing Your network.

HTH

Regards

Giedrius #10257

New Member

Re: OSPF within FR hub and spoke

For the OSPF configuration that you mention above, I do not think that virtual links would be required.

If the main HQ site is area 0, and that each regional site is then its own area, then the need for virutal links is removed.

At that point, we should not be able to minimize the routing updates going to the stub areas with summarization?

Re: OSPF within FR hub and spoke

you can have the HQ site (lan) in area 0 , while every remote site (both frame relay interface and lan interface) in area 1 through 75 for each site. All these can be made stub, which leads to injection of a default static route into each remote router. There would be no need to summarize each network, because, HQ router will be the one who will route for all sites.

New Member

Re: OSPF within FR hub and spoke

If your remote site is not large, so it's very possible that the routing will not exceed 15 hops, so you also just choose RIP (RIP v2 is better) or EIGRP, or OSPF. If you choose OSPF, One area 0 is OK. It's recommended that routers in 1 ospf area do not more than 100 routers. And also pay attention to the config of your frame-relay. If you use point to multipoint, you should also disable split-horizon. Hope this can help you.

Best Regards

Teru Lei

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