OSPF - Stub Networks

Can anyone give me a break down when you would use the different type of Stub Networks?

The FLG book did a fantastic job of telling me what each router does and showing me the big picture but I dont know when I would use one compared to the other for some of them.

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Comments

networker050184

It all depends on your network design.

Stub Area - Use this when you don't need your routers having external routing information and can just use a default route.

Total Stub - Use when you just want a default out of the area.

NSSA - Obviously use this one when you need one of the above and also to inject external routes.

Having less routes to deal with leads to less resource utilization. I've seen quite a few networks set up where every area is a stub except area 0 which works perfectly fine in most scenarios. I prefer to keep external routing info out of your IGP and not have to worry about all of those external routes.

xXErebuS

I'm going to provide you with a link that helped me understand:

OSPF area types - Packet Life

When to use them has more to do with design; for example does a particular area need to know details about internal EIGRP routes (external to OSPF system) that are not connected to it; or does it just need to know how to get out of the OSPF area (default route). Knowing about the EIGRP routes is really unnecessary and eliminating this can speed up convergence and lower the processing overhead of the device (maybe you need a L3 application layer but the switches are low end MLS switches - in this case you can make them totally stubby (just a default route), or if you want them to know about all OSPF routes but not other internal routing (such as EIGRP) stub.

Edit: networker beat me to it; please be careful with NSSA by default they do not advertise a default route so any external (i.e. web requests) are S.O.L. You can use no-summary to fix this...

kohr-ah

Thank you both that helps me a ton!

Dieg0M

xXErebuS wrote: »

Edit: networker beat me to it; please be careful with NSSA by default they do not advertise a default route so any external (i.e. web requests) are S.O.L. You can use no-summary to fix this...

Yes, and remember the no-summary command on an ABR advertises a default route into the NSSA as a type 3 LSA and the default-information originate on an ABR advertises a default route type 7 LSA.