OSPF Wan Design question

[Will Phinney]

Good evening everyone,

I'm deploying an OSPF design and had a question or two:

I'm going to be creating an area 0 for my corporate office, which will be my ABR, and plan on making my other sites area 1 or area 2 for each new site, maybe even just leave everything to area 2 since I won't have that many remote sites. When setting my point-to-point links would you suggest putting those links in area 0 or area 1 or whatever corresponding area that site is in? 

Thanks!

[Meheretab Mengistu]

Hi Will,

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@Will Phinney wrote:

Good evening everyone,

I'm deploying an OSPF design and had a question or two:

I'm going to be creating an area 0 for my corporate office, which will be my ABR, and plan on making my other sites area 1 or area 2 for each new site, maybe even just leave everything to area 2 since I won't have that many remote sites. When setting my point-to-point links would you suggest putting those links in area 0 or area 1 or whatever corresponding area that site is in? 

Thanks!

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If you put the point-to-point links in area 0, you will make the routers on the sites to be ABRs; and I think you do not want to do that. 

I would not put the point-to-point links in area 0. I will prefer to put the remote sites in non-backbone area and configure them, possibly, as  stub areas (or totally-stub -- depending on the case) so that they will receive less LSAs.

HTH,

Meheretab

[Will Phinney]

Thanks you, Meheretab. So you suggest put wan links in area 1, that connect back to the ABR and then make those sites stub areas? I was thinking of making everything a normal area.

[Meheretab Mengistu]

You can make all normal areas.

If you need only default routes to those sites (if the only connection those areas have is through the ABR), you can take advantage of using stub areas. However, if you are planning to use those areas as a transit or not sure whether you will add another site behind some of those sites in the future, configure them as normal areas. I believe it will not have a big impact for small networks.

HTH,

Meheretab

[Will Phinney]

More than anything I was just wondering about the ppp to links and since these are all "remote" offices I'm more interested in the routes from the other sites, so essentially ppp links in area 1 as well as the other remote sites? I could use stubby, but like I said I wanted to just get the advertisements from these sites. I also wanted to plan for the future too though.... 

[Meheretab Mengistu · Accepted solution]

In your case, it will be good to use "normal" areas.

Let's hear if others have different opinion.

HTH,

Meheretab

[Will Phinney]

Thanks! I'll take this in consideration. I don't foresee any issues with using what we described and I would use stubby if I wanted default, but this should get me what I need. Putting wan links in other areas could cause issues.

[Joseph W. Doherty]

Depending on the overall size of your topology, unclear you would truly benefit from an OSPF multi-area design.

[Will Phinney]

@Joseph W. Doherty I was looking over best practices with making sites their own area, remote sites, even if I made them all a single area. Thoughts? I realize I could put everything in area 0, but wanted to think long term and as of right now I won't even come close to the 40-50 benchmark. Just curios. Much appreciated.

[Joseph W. Doherty]

The 40 - 50 OSPF recommendation, for number of routers per area, is both a bit dated and a very rough rule of thumb. Modern network devices can often support an OSPF area with a rather large number of OSPF nodes, especially if they support ISPF.

With modern network devices, if you don't expect to come even close to 40 or 50 nodes, I would suggest you stay with a single area, unless your branch WAN links are very low bandwidth and you're trying to minimize WAN bandwidth consumption for LSAs.

An OSPF multi-area configuration, to fully leverage it, is more complicated.

If you stay with a single area, you also don't have to use area zero.