NSSA and Total NSSA?

Paul Boz

I'm going through the blueprint and noticed that it lists the NSSA and the Totally NSSA. I have studied NSSAs before but in all of my studies I have never even heard of a totally NSSA area. Google gives me nothing and I can't find anything on Cisco's site either. Just using deduction I fail see what a Totally NSSA area is. I can understand a Totally stub, but I don't see any other way for an NSSA to work.

IV. IP Routing

   1. OSPF
         1. Standard OSPF area
         2. Stub area
         3. Totally stub area
         4. Not-so-stubby-area (NSSA)
         5. Totally NSSA
         6. Link State Advertisement (LSA) types
         7. Adjacency on a point-to-point and on a multi-access (broadcast)
         8. OSPF graceful restart
         9. Troubleshooting failing adjacency formation to fail
        10. Troubleshooting of external route installation in the RIB

Can someone clue me in?

EdTheLad

There are two flavors of NSSA, just like stub areas. There are NSSAs that block type 5, but allow type 3 and 4 LSAs, and there are NSSA "totally stub areas," which allow only summary default routes and filter everything else.

Paul Boz

Okay, thanks for clarifying. It's just weird that I'd never seen that before.

GT-Rob

Odd that you made it through BSCI without hearing about it. Its mentioned serveral times in all the material.

freefly_27

EdTheLad wrote:

There are two flavors of NSSA, just like stub areas. There are NSSAs that block type 5, but allow type 3 and 4 LSAs, and there are NSSA "totally stub areas," which allow only summary default routes and filter everything else.

NSSA's convert type 5 lsa's to type 7 lsa's at the abr and vice versa

icejam

**hint** configure this command on NSSA ABRs only

OSPF Not-So-Stubby Area (NSSA) [IP Routing] - Cisco Systems

shodown

GT-Rob wrote: »

Odd that you made it through BSCI without hearing about it. Its mentioned serveral times in all the material.

Not true. They don't mention it in the BSCI book. I just double checked to make sure. I encountered it in the Troubleshooting IP protocols book.

stuh84

shodown wrote: »

Not true. They don't mention it in the BSCI book. I just double checked to make sure. I encountered it in the Troubleshooting IP protocols book.

Which BSCI book did you read? Both of the Cisco Press ones mention them, or at least the Exam Certification guide and the Self Study guide.

I don't have the books to hand (they are at work, I am at home), but I do have my notes I made from the books (and these were from the books ONLY, no outside information in these notes), and in the one I have for the Exam Guide Notes I see under "Chapter 8 - OSPF Advanced Topics" a title for Not-So-Stubby Areas, with mentions of NSSA and Totally NSSA.

So unless you've been working from books before the current/being-phased-out version of the CCNP, I don't see how it could be missed.

ColbyG

Here's a table and diagram I created from Narbik's bootcamp:





These helped me a lot with understanding the different areas.

shodown

stuh84 wrote: »

Which BSCI book did you read? Both of the Cisco Press ones mention them, or at least the Exam Certification guide and the Self Study guide.

I don't have the books to hand (they are at work, I am at home), but I do have my notes I made from the books (and these were from the books ONLY, no outside information in these notes), and in the one I have for the Exam Guide Notes I see under "Chapter 8 - OSPF Advanced Topics" a title for Not-So-Stubby Areas, with mentions of NSSA and Totally NSSA.

So unless you've been working from books before the current/being-phased-out version of the CCNP, I don't see how it could be missed.

I have the study book not the exam book for the 901 exam and on page 248 where they mention the special area types they don't mention totally nssa. They mention totally stub and NSSA, but not totally nssa. I encounted it in other cisco books, bu tthis one its not there.

stuh84

Is it not mentioned as nssa no-summary? I'm surprised at such a glaring omission, especially given I saw today the Self Study guide from back in 2004 on someones desk at work, and it mentions them in there.

shodown

stuh84 wrote: »

Is it not mentioned as nssa no-summary? I'm surprised at such a glaring omission, especially given I saw today the Self Study guide from back in 2004 on someones desk at work, and it mentions them in there.

I don't have my book in front of me now. I keep those at work. I just have TCP/IP vol 1 and 2 at home.

jason_lunde

Thanks for those charts colby. I think you posted those on your blog a while back and I never grabbed them, but I've got them now. They straitened lsa's out for me pretty quickly. Appreciate it.

SysAdmin4066

I definitely remember NSSA Totally Stub areas being discussed in the BSCI curriculum.

BADfish10

colby thank you that is brilliant

yuriz43

ColbyG wrote: »

Here's a table and diagram I created from Narbik's bootcamp:

These helped me a lot with understanding the different areas.

Great diagram!


In case anybody is wondering, NSSA Stub is configured on the ABR by the following:

area 4 nssa default-information-originate metric 20

The books don't really go over this type much. But its good to know. I have assumed in the past that an NSSA would advertise a default route for Type 5 LSAs from other areas, but it DOESN'T. You need the above command in order to do so. no-summary of course will accomplish the same thing, but will also suppress type 3 LSAs.


Thanks Colby!

ColbyG

An NSSA ABR won't inject a default route by... default (lol). You use the "area n nssa default-information-originate" command to inject the default from the ABR.