Metric shouldn't have anything to do with it. Whether I'm using RIP or OSPF
the default route is being added to the routing table of the hub router.
The issue is that with no ip classless configured, the hub router should NOT
ever pick the default route when trying to reach unknown subnets of the
10.x.x.x network.
In my case, when RIP installed the default route it behaves correctly. When
OSPF installed the route it behaved as if 'ip classless' were configured.
Very odd.
John
> I guess in faovour of metric.
>
> "John Neiberger" <[EMAIL PROTECTED]> ���g��l��
> [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > Okay, I just tried this with RIP advertising the default route and I'm
> even
> > more confused! Now, it behaves as I would expect. With no ip
classless,
> > pings to unknown 10.x.x.x subnets are unroutable even though there is a
> > default route in the routing table.
> >
> > With no ip classless, why does my router take the default route when it
> was
> > installed by OSPF but not when it was installed by RIP? I would expect
it
> > to never take the default route for 10.x.x.x addresses with no ip
> classless.
> >
> > This really concerns me because I was taking a practice CCIE written
exam
> a
> > few days ago and ran across a question like this and I answered the
> question
> > assuming normal behavior of no ip classless and got it right. Now I'm
> > thinking there are some more twists to its behavior that i'm not aware
of.
> >
> > John
> >
> > > Sure, I'll try that but I don't see why it should matter. As I
> > understand
> > > it, ip classless affects routing table lookups only and it doesn't
care
> > how
> > > those routes were installed into the table.
> > >
> > > Although, given this behavior, my assumption might be wrong.
> > >
> > > Thanks,
> > > John
> > >
> > > > John,
> > > > Interesting. I think this is due to OSPF, not redistribution
> problem.
> >
> > > Can you try running RIP instead of OSPF ?
> > > >
> > > > Cheers,
> > > > YY
> > > >
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
Behalf
> Of
> > > > John Neiberger
> > > > Sent: Sunday, March 25, 2001 5:28 AM
> > > > To: [EMAIL PROTECTED]
> > > > Subject: IP Classless Revisited (this is just odd...)
> > > >
> > > >
> > > > Ok, just when you thought it was safe to go back in the water....
Or
> > > should
> > > > I say, just when I thought I understood the behavior of 'ip
> classess'
> > and
> > > > 'no ip classless'.... Let me summarize my lab setup.
> > > >
> > > > RouterA-----RouterB------RouterC
> > > >
> > > > Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24. OSPF
is
> > > running
> > > > on both links. 'ip classless' is on A and C, but not B
initially.
> On
> > B
> > > I
> > > > see these routes:
> > > >
> > > > 10.0.0.0/24 is subnetted, 2 subnets
> > > > C 10.1.2.0 is directly connected, Serial1
> > > > C 10.1.1.0 is directly connected, Serial0
> > > >
> > > > That's what I expect to see. Then I add a default route on B,
'ip
> > route
> > > > 0.0.0.0 0.0.0.0 10.1.1.2'. With no ip classless configured, any
> > packets
> > > to
> > > > unknown subnets of 10.0.0.0/8 should be dropped. I tested it and
> that
> > is
> > > > the case. With 'ip classless' configured, and unknown packets
> > regardless
> > > of
> > > > major network get routed to 10.1.1.2.
> > > >
> > > > Now here is what I don't understand. Let's turn off ip classless
on
> B
> > > > again, then go to Router C and add a default route to null0 and
> > > > default-information originate to the ospf process. I now see
this
> in
> > > router
> > > > B:
> > > >
> > > > 10.0.0.0/24 is subnetted, 2 subnets
> > > > C 10.1.2.0 is directly connected, Serial1
> > > > C 10.1.1.0 is directly connected, Serial0
> > > > O*E2 0.0.0.0/0 [110/1] via 10.1.2.2, 00:06:38, Serial1
> > > >
> > > > There is indeed a default route. With no ip classless
configured, I
> > > would
> > > > expect the same behavior as before. If I were to ping 10.5.5.5
the
> > > packets
> > > > should be unroutable, but they're not! They get routed to the
> default
> > > route
> > > > whether or not ip classless is configured.
> > > >
> > > > Why is a default route learned through a routing protocol treated
> > > > differently than a manually configured default route? I went
> through
> > > this
> > > > entire process twice and I just don't understand the behavior.
> > > >
> > > > What am I missing? I know it's going to be something obvious,
but I
> > > don't
> > > > see it yet.
> > > >
> > > > Ok, I just now tried this: with the ospf external default route
> still
> > in
> > > > the routing table, I pinged 10.5.5.5 and it took the default
route.
> > Then
> > > I
> > > > manually added a default static route and the destination became
> > > unroutable
> > > > due to 'no ip classless' being configured. Removing the static
> > default
> > > it
> > > > becomes routable again.
> > > >
> > > > Weird. What's going on?
> > > >
> > > > Thanks,
> > > > John
> > > >
> > > >
> > > >
> > > >
> > > >
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