I know I haven’t posted much lately, with studying for the Cisco BSCI and working on my kitchen floor, but I always get a bit of a kick when reviewing OSPF routing protocol, specifically when talking about stub areas. This is because of the naming of these various types of stub areas:
Stub Area
Totally Stubby Area
Not So Stubby Area (NSSA)
Totally Stubby Not So Stubby Area (sounds kinda contradictory, doesn’t it)
That’s a lot of subbiness going on here. What is it all about, anyway? In a nutshell, the various stub areas in OSPF are configured as such to limit the types of LSA (link-state advertisements) that the router receives, reducing its routing table size. The particulars of each type are a lot to get into in a post, but visit Cisco’s site on the topic to learn more.
Luckily the configuration itself is fairly straightforward. All commands are within the OSPF router config mode.
For a stub area:
area area-id stub (where area-id is the number label of the area in question)
For a Totally Stubby Area:
area area-id stub no-summary (no-summary only required if it is on an Area Border Router, or ABR)
For the Not So Subby Area
area area-id nssa
And for Totally Stubby Not So Stubby Area
area area-id nssa no-summary (again, no-summary only required on an ABR)
Of course, as stated, there’s a bit more to it, but Cisco generally does a good job with information on various topics on their web site. The article also mentions Virtual Links. All areas in an OSPF network are required to be connected to Area 0 (the backbone area). Virtual links are a sort of “band-aid” you can use when an OSPF area cannot be physically connected to Area 0.
So you’re probably wondering why I haven’t posted on my Kubuntu install yet. Well, it’s because I’ve been spending most nights studying for the CCNP BSCI exam (BCSI – Building Scalable Cisco Internetworks, essentially the routing exam). My CCNA expires in June, so I’ve set out to try and pass one at the CCNP level to keep current. I’ve gone through the EIGRP and part of OSPF modules (I’m most familiar with OSPF, as that is the routing protocol of the last two customers I have done work for). My question, for anyone reading this: Is there a practice exam software that you recommend? In the past I’ve tried Boson and Self Test, but just wanted to get everyone’s thoughts on what is out there today that they find are good. I find the practice tests a good way to find out what I know, and what I need to focus on…
The Science Attic 