I guess in faovour of metric.
"John Neiberger" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó
[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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>
>
>
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