Subject: Question about NSSA

From: Mani Devarajan <[email-masked]>
Date: Thu, 12 Sep 2002 11:09:13 -0700

Hi all,
                                   ASBR
      -----     -----     -----    -----     -----
     |     |   |     |   |     |  |     |   |     |
     | R1  |   | R2  |   |  R3 |  |  R4 |   | R5  |
     |     |   |     |   |     |  |     |   |     |
      -----     -----     -----    -----     -----
          |     |   |      |  |     |  |     |
           -----     ------    -----    -----
           AREA1     AREA 0    AREA2    RIP Network

If I configure for the above setup and do a redistribution
on ASBR, R1 will recieve the type-5 LSA for the externa
network. In that case rechability between R1 and R5 is working
fine.

If I change the Area2 to NSSA but I dont load the config
for redistribution on the NSSA ASBR(R4), does the external
rip network will be still reachable from the R1(as it has
the type5 LSA in its LSD)

Thanks in advance,
Mani

---

From: "Pat Murphy - (650)329-4044" <[email-masked]>
Date: Thu, 12 Sep 2002 14:42:20 -0700

Mani,

> 1 - if redistribution is not disabled, then R3 will
>     translate the type7 to type5 LSA and inject it in to
>     backbone. So that connectivity is not broken in between
>     R1 and R5.

Correct.

> 2 - if redistribution is disabled, R4 will flush the
>     type 4 and type5 LSA which it generated previously.
>     So that R1 will not be able to reach the external
>     network.

There is no relationship between the disabling of
redistribution and the flushing of the standard area's type 4
and type 5 LSAs. The latter should be done regardless when
the area type is changed to NSSA. Assuming they are flushed
(again it depends on the completeness of the implementation)
the disabling of redistribution will prevent R1 from reaching
the original Type 5 LSA's network through R4, as there won't
be a Type 5 LSA for the network with a forwarding address
from R4.

Pat