From: P729 (p729@xxxxxxx)
Date: Fri Jul 12 2002 - 21:37:26 GMT-3
Unlike discontiguous wildcard masks, I don't believe the parser supports
discontiguous subnet masks (IIRC, it wasn't explicitly forbidden early on
but I think it's actually advised against [if not forbidden] in later
revisions of the RFC) so it probably took the 0.0.0.255 as 0.0.0.0, which in
turn made the first argument all networks, hence 0.0.0.0/0. Did the
'summary-address 152.1.11.0 0.0.0.255' command remain as you entered it when
you looked at the running config? It would be interesting to see if masks of
0.0.255.255, 0.255.255.255 and 127.255.255.255 produce the same results...
Regards,
Mas Kato
https://ecardfile.com/id/mkato
----- Original Message -----
From: "Mayande P.Gowon" <bustahnet@usa.net>
To: <ccielab@groupstudy.com>
Cc: <mayande@itochu.net>
Sent: Friday, July 12, 2002 10:58 AM
Subject: summary-address creates default gateway
> I'm hoping someone will be able to provide me with some insight
> on the following:
> I was working on a redistributing IGRP & OSPF lab the other night when I
came
> across something that I'm unclear about any thoughts or explanations would
be
> appreciated:
>
> lo0--A----B----C-----D----lo0
> There were 4 routers - A, B, C, D. The serial interfaces between A & B are
in
> OSPF area 1, the serial interfaces between B & C are in OSPF area 0, and
the
> link between C and D are IGRP.
> This is a VLSM/FLSM scenario (IGRP has /24 mask, and OSPF has various).
The
> lo0 of A is being redistributed (redistribute connected subnets) into
OSPF,
> because it is a /28 I performed a summary-address command to advertise it
as a
> /24 to IGRP. All of this worked fine in the end without issue...but the
first
> time I performed the summary command I accidently used the wrong subnet
mask.
>
> Instead of "summary-address 152.1.11.0 255.255.255.0" I typed
> "summary-address 152.1.11.0 0.0.0.255". This created a default null route
> (0.0.0/0) which propogated across the entire OSPF network! In other words
> routers B and C now had a default gateway pointing to the null route
0.0.0.0/0
> on router A.
> This seems like a neat trick as this default gateway gets propogated
across
> the OSPF network and without creating a static route. I however don't
really
> understand what caused this to happen...any insight?
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:28 GMT-3