From: Padhu (LFG) (padhu@xxxxxxxxxxxx)
Date: Fri May 25 2001 - 14:26:55 GMT-3
Sorry about the IP swaps...But just from my memory , immaterial of whatever
you redistcribute with ospf,the "locally attached ospf configured network"
will not propogate untill the mask is
chosen this way.My lab is offline .. Pls let me know what your findings are.
I always thought 0.0.0.0 narrows it down so much...but thats the side
effect.
The other thing i fail to understand is that, the local interface on the
ASBR even though is
configured for ospf will not propagate into eigrp/igrp/rip/isis or
whatever...Routes marked with a "O" only get redistributed. The local
interface attached to an area is considered connected as far as the ASBR is
concerned...So redistribute connected into eigrp/igrp/rip/isis fixes that.
Cheers,Padhu
-----Original Message-----
From: Walter Chen [mailto:wchen@iloka.com]
Sent: Friday, May 25, 2001 12:22 PM
To: 'Jim Graves'; Padhu (LFG); ccielab@groupstudy.com
Subject: RE: Another redistribution/connected question
While in your diagram, 10.2.3.0/24 belongs to IGRP domain instead of OSPF
domain. So what you should play with is 10.1.2.0/24. If you do, you'll be
surprised to find that this network will not be redistributed into IGRP if
you use method 2, i.e., the /32 mask. Go figure.
Walter
-----Original Message-----
From: Jim Graves [mailto:jtg@lucent.com]
Sent: Friday, May 25, 2001 12:52 PM
To: Padhu (LFG); ccielab@groupstudy.com
Subject: RE: Another redistribution/connected question
I haven't tried that. I'll give that a shot later.
I'd be amazed if it made a difference though, for two reasons. First, I
almost never use the second method you describe for putting OSPF interfaces
in areas, so I wouldn't see the results of it. But more than that, as far
as I'm aware the only thing the OSPF network command does is put interfaces
in areas. The mask has nothing to do with the area itself--it's just a
convenient way to match more than one interface address.
Is there a reason you think this would make a difference?
(Might as well save a step, because if I do this and it makes a difference,
my next question will be: why?)
Thanks,
Jim
At 11:15 AM 5/25/2001 -0500, Padhu (LFG) wrote:
>On r2 can you try the ospf config with these 2 methods and see if you see
>different results ?
>
>Method-1:
>R2
>router ospf 100
>network 10.2.3.0 0.0.0.255 area 0
>
>Method-2:
>R2
>router ospf 100
>network 10.2.3.1 0.0.0.0 area 0
>
>Cheers,Padhu
>
>
>-----Original Message-----
>From: Jim Graves [mailto:jtg@lucent.com]
>Sent: Friday, May 25, 2001 9:42 AM
>To: ccielab@groupstudy.com
>Subject: Another redistribution/connected question
>
>
>I've been playing with redistribution some more, and I've run into some
>behavior I can't quite explain. I've noticed that sometimes when
>redistributing, a connected network won't make it in with the rest of the
>routing protocol's domain; sometimes it does.
>
>For example: Suppose we have:
>
>(OSPF
>[10.1.0.0/24]---R1---[10.1.2.0/24])--R2---([10.2.3.0/24]---R3---[10.3.0.0/2
4
>]
>IGRP)
>
>R2 does redistribution between OSPF and IGRP.
>
>Sometimes when I've done this, the connected network (10.2.3.0 in this
>example) goes into the ospf domain without anything else needing to be
>done. Sometimes, though, I need to redistribute it into the OSPF domain
>explicitly. I haven't been able to play with this quite enough to know
>what makes the difference. Does anyone know? Is it related to which
>protocol is used (IGRP vs. RIP, say)? Does it have to do with whether
>redistribution is controlled with route-maps? I plan to test these two
>theories if I have time.
>
>Another question: in scenerios like I describe above where the routing
>domains look like stubs off of each other (i.e., there's only one
>redistribution point between two protocols; it looks like a tree), is
>split-horizon enough to prevent route feedback? I used to put in
>route-maps to control redistribution as a matter of habit, but now I'm
>concerned about having them counted as "extra" commands (although I can
>also give a pretty good "belt and suspenders" speech if needed). More
>recently, I've just used split-horizon to prevent route feedback. That
>seems to be working, but I might also be missing something.
>
>Finally, does anyone have a good, really in-depth resource on
>redistribution? I've read Doyle v1, but I'm looking for something that
>goes into the guts of how redistribution works. For starters, I'm still
>not clear on exactly where the redistributed routes come from. Are they
>routes that are in the routing table? Are they routes that are in the
>database? Or does it depend on the routing protocol -- OSPF takes the
>routes straight from the database, while IGRP or RIP have no database, so
>they have to take routes straight from the routing table (which would also
>explain my confusion about connected routes)?
>
>Lots of questions, I know. I have less than a week before my test, and I'm
>dissecting redistribution. :)
>
>Thanks all,
>
>Jim
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