From: Peter van Oene (pvo@xxxxxxxxxxxx)
Date: Thu Jan 03 2002 - 02:51:01 GMT-3
OSPF networks have a few major scaling problems. The main one is that type
5 LSA (external) flood throughout the entire OSPF domain. What this means
is that no matter how many areas you create, your type 5's still require
processing by all your routers. In order to constrain this, you can
create stub areas which restrict the flow of type 5's and type 4's such
that the routers in the area need not to worry about processing type
5's. However, what happens when you want to push some statics into an
area that you have designated at stub? Essentially, you've decided that
there is no value in flooding a mess of external information into the area,
however, you'd still need to get these few externals into OSPF in that
area. Without NSSA you'd have to make the area a normal stub area and
you'd be able to get your few new type 5's in but would also get all of the
type 5's from the rest of the OSPF domain. However, by making it an NSSA,
you have the ability to inject these few new externals as type 7's (which
look like 5's, just with another name) without having to absorb all of the
type 5's you didn't want in the first place. These 7's get translated into
the rest of the normal OSPF domain at Type 5's all is good.
NSSA is a very common option in OSPF networks and is definitely worth some
study time.
Hope this helps.
Pete
At 07:30 PM 1/2/2002 -0800, Bhisham Bajaj wrote:
>Hi
>
>I am trying to understand the concept of NSSA area
>
>I tried to read a few doc on it but did not help
>
>Can some one explain me this or guide me to some good
>link for it
>
>Thank u
>bhisham
>
>
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