From: Mayande P.Gowon (bustahnet@xxxxxxx)
Date: Fri Jul 12 2002 - 14:58:22 GMT-3
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 - 19:36:27 GMT-3