Benefits and Use case of Stubby and NSSA

Hey guys,

What is the benefits of a Stubby and NSSA setup for LSA's with OSPF?

Like I understand with a NSSA it goes from a Type 7 into the NSSA network, say area 1 (as shown in the picture is the NSSA), and then goes to the stubby ASBR router into Area 0 as Type 5. But what I'm looking to grasp is what is the core purpose of using this kind of OSPF in a network vs just using normal OSPF?

Like what is the benefit of "O IA" vs "O E2"; I'm used to seeing "O IA" so I'm looking to see what would be the benefits of the other types. Like for E2 or E1, what benefits do these provide for routing? ... route shaping, less traffic at core?

I'm probably getting way too deep into CCNP levle stuff but I'm really looking to grasp this information to better understand OSPF.

ospf NSSA 1.jpg

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Comments

shodown

Been a long time since I've been doing WAN work using OSPF, but back in the day, we used them to keep the routing tables small. On the network I was working we had around 700 sites on our own private link lan so keeping the routing table small as you can just get 1 route in the area.

Deathmage

Having a CCIE showing me it in Google Hangouts. Meet him on Facebook, he's been a world of help thus far....

discontigious area setup...

nice having a CCIE as a friend.....jpg

discontgious areas setup.jpg

OfWolfAndMan

Seems like your buddy has showed you a few things, but here's what I got for you:
1.Stub areas filter LSA type 4 & 5
2. Total Stub filters type 3, 4, and 5.
how do the stub routers know how to get out of the area you ask? The ABR advertises a default route. This is useful in the situation where you have a router not acting as a transit for other networks and it has limited hardware resources (Or you're pushing your LSA limitations).
3. NSSA and Total NSSA filter the same things as above, however they are meant for those places where you are redistributing an external AS into a non-area 0 area. Say for example your company acquires a company's infrastructure and it attaches to your area 1. Migrating this piece is too tedious rolling it to the backbone area, so instead you just patch an NSSA in between. Like GRE, it's more of a "network duct tape" in my opinion. However, there are additional use cases...

Deathmage

OfWolfAndMan wrote: »

Seems like your buddy has showed you a few things, but here's what I got for you:
1.Stub areas filter LSA type 4 & 5
2. Total Stub filters type 3, 4, and 5.
how do the stub routers know how to get out of the area you ask? The ABR advertises a default route. This is useful in the situation where you have a router not acting as a transit for other networks and it has limited hardware resources (Or you're pushing your LSA limitations).
3. NSSA and Total NSSA filter the same things as above, however they are meant for those places where you are redistributing an external AS into a non-area 0 area. Say for example your company acquires a company's infrastructure and it attaches to your area 1. Migrating this piece is too tedious rolling it to the backbone area, so instead you just patch an NSSA in between. Like GRE, it's more of a "network duct tape" in my opinion. However, there are additional use cases...

Thanks man!

CCIE #50693