From: Ian Blaney (ian.blaney@gmail.com)
Date: Sat Nov 11 2006 - 09:07:00 ART
Michael
OSPF NSSA
0 20 EIGRP
R1-----------R2----------R3--------R4
In the above R1 and R2 are connected to the backbone. R2 is also a ABR
between area 0 and the NSSA 20. A NSSA allows you to redistribute external
routes into a stub area so in the above R3 is an ASBR redistributing EIGRP
routes from R4 into NSSA 20. The routes will enter as type 7 and be
translated to normal external type 5 on R2 and then sent into the backbone.
This is the normal way a NSSA works.
If we add another router to the picture
OSPF NSSA
0 20 EIGRP
R1-----------R2----------R3--------R4
|
| RIP
|
R5
R2 is now redistributing RIP routes from R5. R2 is now an ASBR and a ABR
between the backbone and the NSSA 20. With the specal case of R2 being an
ABR/ASBR this is where the no-redistribute comes in to play. By default R2
will send the external RIP routes into the NSSA 20. When you add the
no-redistribute option R2 will no longer advertise the RIP external routes
into the NSSA.
I think you are getting confused with the redistribution on R3. As I said
no-redistribute will be only used in the special case where the router is
both an ASBR and ABR.
I hope this is a bit clearer. Try and lab it up. If you are still confused I
can do it myself and send some outputs.
Ian
On 11/10/06, Michael Zuo <mzuo@ixiacom.com> wrote:
>
> Hi Group,
>
>
>
> Anyone knows the difference between:
>
>
>
> Area 1 nssa no-summary no-redistribution
>
>
>
> And
>
>
>
> Area 1 stub no-summary
>
>
>
>
>
> To me, they seem to be the same thing...
>
>
>
>
>
> thanks
>
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