From: Mike Gutknecht (mike@xxxxxxxxxxxxx)
Date: Mon Jun 18 2001 - 02:53:56 GMT-3
Without seeing the configs, I think that Router A does not have Area 2
configured as an NSSA. It would then inject the EIGRP routes into OSPF as
Type 5's rather than type 7's. Because B is configured for Area 2 NSSA, it
drops the type 5 LSA.
Now Router C is an NSSA-connected ABR and an ASBR, in this case the default
behavior is to advertise the external routes (3.0.0.0/8) into the NSSA as
type 7's. You can prevent this by adding the "no redistribution" keyword on
the NSSA area statement on router C. See Doyle, p539.
To me, this is as complicated as OSPF gets. Unless you want to create a GRE
tunnel through area 2, give it IP addresses, and add its network to area 0.
;^)
-Mike G
-----Original Message-----
From: Peter Van Oene [mailto:pvo@usermail.com]
Sent: Wednesday, June 13, 2001 8:54 AM
To: Don Dettmore; ccielab@groupstudy.com
Subject: Re: nssa question
>From what I can tell on a quick read this looks normal. Area 2 is a stub
area and thus won't see the type 5 external that contains the 192 prefix,
while it correctly see's the type 7 3/8 advertisement.
*********** REPLY SEPARATOR ***********
On 6/13/2001 at 10:36 AM Don Dettmore wrote:
>Ok, go with me on this one - I thought NSSA areas were quite easy, but
>apparently I don't understand them:
>
>(192.168.49.0)-----RouterA---(172.16.253.0)---RouterB-----(2.2.2.0)-----Rou
te
>rC-----(3.0.0.0)
>
>Router C runs:
>- EIGRP 3 on the 3.0.0.0 interface
>- OSPF Area 2 on the 2.2.2.0 interface
>- OSPF Area 0 on all other interfaces (not shown in diagram)
>
>Router B runs OSPF Area 2 on all interfaces
>
>RouterA runs:
>- OSPF Area 2 on the 172.16.253.0 interface
>- EIGRP 25 on the 192.168.49.0 interface
>
>Area2 is an NSSA area. RouterC is configured to originate a default route
>into Area 2 (command= area 2 nssa default-information-originate)
>
>I am redistributing the following routes into OSPF:
>- 3.0.0.0 on RouterC
>- 192.168.55.0 on RouterA (this is a network that exists out in the EIGRP
>25
>domain)
>
>What I don't understand is the routing table on RouterB. It contains the
>following:
>- A route (N2) to 3.0.0.0. It shouldn't have this, should it?
>- No route at all to 192.168.55.0, though this route exists on RouterC as
>an
>N2 route
>
>I thought it should be reverse - RouterB would see 192.168.55.0 as an N2
>route
>(type 7LSA) and no route to 3.0.0.0 - a default route instead. (it DOES
>see
>the default route).
>
>Note that other Area 0 routers further down the chain (not shown on the
>diagram) properly see both 3.0.0.0 and 192.168.55.0 as E2 routes.
>
>Can anyone explain this?
>
>TIA
>
>Don Dettmore
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