From: Yasser Abdullah (yasser@alharbitelecom.com)
Date: Mon Jun 07 2004 - 09:14:39 GMT-3
Another option would be to 'virtually' (GRE or VL) connect area 0 of both
routers over the FR and then modify the cost to prefer it.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Richard Dumoulin
Sent: Monday, June 07, 2004 2:57 PM
To: Carlos G Mendioroz
Cc: John Underhill; David Sanchez; ccielab@groupstudy.com
Subject: RE: OSPF internal vs External
Yes, I have realised I had an error of concept. I have taken the habit of
modifying the distance without thinking about it anymore. I'll have to go
back to my CCNA days :)) Basics basics !!
So even changing the metric won't work !?!? I see it as a limitation of
Cisco ospf implementation then. In the scenario described below it was not
an option to filter a route because I needed to chose one over the other
when both were present.
Even if it is a bad design, I would have liked to have the option of
preferring the intra vs the interarea route !!
--Richard
-----Original Message-----
From: Carlos G Mendioroz [mailto:tron@huapi.ba.ar]
Sent: lunes, 07 de junio de 2004 13:38
To: Richard Dumoulin
Cc: John Underhill; David Sanchez; ccielab@groupstudy.com
Subject: Re: OSPF internal vs External
OSPF will always prefer the interarea route to the IA, and that comes
before the metric plays a role, and much before the distance plays a role.
You can change distance, and distances associated with some routes
learned from one particular neighbour, but distance is going to be used
for discerning different "protocol" routes. As this routes come all from
the same protocol, distance will be no help.
You can also change specific metric, but it won't help, because no
matter what distance, intra area routes will win over IA.
One way to do that is to filter out the intra area route (using
distribute-list in ) so only the IA route is available.
Richard Dumoulin wrote:
> I forgot to mention that B's loopback is in area 0 !!
>
> -----Original Message-----
> From: Richard Dumoulin
> Sent: lunes, 07 de junio de 2004 3:28
> To: John Underhill; David Sanchez; ccielab@groupstudy.com
> Subject: RE: OSPF internal vs External
>
>
> Actually it was a scenario where I needed to prefer an interarea route
> vs an intraarea one. Suppose you have 2 routers, A and B connected via
> frame-relay and isdn. Dialer watch is configured. A will dial B if it
> loses B's loopback. Now the frame-relay link is in area 1 and the isdn
> in area 0. When the frame-relay goes down, dialer watch triggers a
> call and A learns B's loopback. When the frame-relay comes back, A
> never installs the interarea B's loopback address because it still
> prefers it through the isdn. A consequence is that the isdn stays up
> indefinitely. I know it's a bad design but it is only an exercise :)
>
> --Richard
>
> -----Original Message-----
> From: John Underhill [mailto:stepnwlf@magma.ca]
> Sent: lunes, 07 de junio de 2004 2:26
> To: Richard Dumoulin; David Sanchez; ccielab@groupstudy.com
> Subject: Re: OSPF internal vs External
>
>
> I am trying to envision the circumstance where this would be
> plausible, or desirable.. the destination network is either within the
> ospf domain or it is an external route.. but how could it be both? But
> I suppose you could manipulate the metric with an inbound distribute
> list calling a route map, then in the route map filter on route source
> | interface | or route type, and use the set metric command to apply
> the new metric.. or for that matter filter the undesirable route
> completely using a similar method. Never tested it, but it's worth a
> look.
>
> router ospf 199
> distribute-list route-map MYFILTER in
> !
> route-map MYFILTER permit 10
> match route-type external
> set metric 80
>
> Here's a good link..
> http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_featur
> e_guid
> e09186a008012db77.html
>
> ----- Original Message -----
> From: "Richard Dumoulin" <richard.dumoulin@vanco.es>
> To: "David Sanchez" <david.sanchez@starmedia.com>;
<ccielab@groupstudy.com>
> Sent: Sunday, June 06, 2004 8:01 PM
> Subject: RE: OSPF internal vs External
>
>
>
>>In a scenario I did some time ago, I only wanted to prefer one
>>external route not all. I tried the distance command with an acl but
>>in vane. It's true that I did not think about this one. I'll try it
>>when I have time,
>>
>>Thanks,
>>
>>--Richard
>>
>>-----Original Message-----
>>From: David Sanchez [mailto:david.sanchez@starmedia.com]
>>Sent: lunes, 07 de junio de 2004 2:57
>>To: ccielab@groupstudy.com; Richard Dumoulin
>>Subject: RE:OSPF internal vs External
>>
>>
>>You can use the command "distance ospf external 100" to change the
>>administrative distance for only external routes and make them
>>prefered
>
> over
>
>>internal
>>
>>Regards
>>
>>Is there a way for a router to prefer an external ospf route over an
>>Inter area one ? I remember having tried once with the distance
>>command but in vane :( Maybe by manipulating the metrics of the
>>redistributed routes ?
>>
>>--Richard
>>
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>
> ______________________________________________________________________
> _
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-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
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