From: James Simons (ccie.jimmy@gmail.com)
Date: Sat Apr 15 2006 - 20:20:57 GMT-3
On my pod, I am running 12.2(15)T17 with 2621 (non-XM) routers. On some of
the other pods are using 1760s with 12.3T.
thanks,
Jimmy
On 4/15/06, Faryar Zabihi (fzabihi) <fzabihi@cisco.com> wrote:
>
> What image are you runnin on the pods?
>
>
>
> -----Original Message-----
> From: James Simons [mailto:ccie.jimmy@gmail.com <ccie.jimmy@gmail.com>]
> Sent: Sat Apr 15 15:25:26 2006
> To: Schulz, Dave
> Cc: ZeroFlash; Brian Dennis; Aaron Pilcher; Faryar Zabihi (fzabihi);
> Cisco certification
> Subject: Re: OSPF route preferencing
>
> Ok,
>
> It seems that my original post was not clear enough in terms of the
> specific
> problem I was facing. I was originally just looking for the theory behind
> preferencing inter and intra-area routes. But I made some new discoveries
> and I figure I should share them.
>
> The original problem comes off of Internetwork Experts core lab #9. In
> this
> lab, we have two routers, R4 and R5. These routers are directly connected
> with a ppp connection (we will call these interefaces S1). they are also
> connected via a second interface that goes into a frame-relay cloud (these
> interfaces will be called S0). both routers have frame-relay map
> statements
> for the layer 3 to layer 2 mappings for this connection. I was told to
> apply ospf to both routers and have the ppp connection (S1) and the
> loopbacks of both routers in area 0. Then I had to put the frame
> connections (S0) in area 1245. After all that, I was told that each
> router
> should route to the other router's loopback, not through the PPP
> connection,
> but through the frame cloud. For the life of me I could not get this to
> work
>
> I didn't understand how you were supposed to route from area 0 through a
> transit area back to area 0 and have that prefered over the intra-area
> route
> through the PPP connection. The IE solution was to increase the cost of
> the
> PPP interfaces (S1). I tried that and it didn't work. It also made no
> sense how that it could work anyway. So I had some colleagues test it out
> on their pods and they got it to work fine by changing the ospf cost. For
> some reason, the inter-area route through the frame cloud was listed in
> the
> routing table (even though it shouldn't be) as an equal cost path to the
> loopback interfaces. So increasing the cost of the S1 interface
> accomplished the task. After going back over this several times as a
> group,
> we all made sure that our configs were exactly the same. We all felt that
> the behavior of my routers is correct according to how OSPF should work
> but
> their router's behavior was correct according to the IE solution.
>
> All of this leads me to believe that OSPF is not implemented exactly the
> same from IOS version to IOS version. I would have thought that the code
> for OSPF is very stable and is not prone to changing but since the only
> difference between the pods we tested it out on is IOS, then that is our
> only conclusion.
>
> Hope this helps. And let me know if you have any other theories for why
> this occured.
>
> cheers,
>
> Jimmy
>
> On 4/15/06, Schulz, Dave <DSchulz@dpsciences.com> wrote:
> >
> > If we are looking to change the preference for the route (intra and
> > inter-area routes), why not simply change the distance between the type
> in
> > the specifc router? Just a thought.
> >
> > Dave
> >
> > ------------------------------
> > *From:* nobody@groupstudy.com on behalf of ZeroFlash
> > *Sent:* Fri 4/14/2006 10:49 AM
> > *To:* 'Brian Dennis'; Aaron Pilcher; ZeroFlash; Faryar Zabihi (fzabihi);
> > James Simons; Cisco certification
> >
> > *Subject:* RE: OSPF route preferencing
> >
> > Brian --
> >
> > PBR does not answer the question as you stated, but creating a tunnel
> via
> > tunnel interfaces or virtual-links can change the route decision process
> > inside the OSPF process, correct?
> >
> > Depending on the area that the tunnel interfaces are..
> >
> > ZeroFlash
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com
[mailto:nobody@groupstudy.com<nobody@groupstudy.com>
> <nobody@groupstudy.com>]
> > On Behalf Of
> > Brian Dennis
> > Sent: Friday, April 14, 2006 10:39 AM
> > To: Aaron Pilcher; ZeroFlash; Faryar Zabihi (fzabihi); James Simons;
> Cisco
> > certification
> > Subject: RE: OSPF route preferencing
> >
> > Of course you can use all kinds of methods to have the "routing table"
> > prefer one route over another but that wasn't the question. The
> > question was basically asking if inter-area routes can be preferred to
> > intra-area routes. With PBR you are overriding the routing table but
> > not changing the route selection process within OSPF itself. The
> > problem I have with your answer is that people will now assume that they
> > can get PBR to have OSPF select inter-area routes over intra-area routes
> > which isn't true.
> >
> > Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
> > bdennis@internetworkexpert.com
> >
> > Internetwork Expert, Inc.
> > http://www.InternetworkExpert.com
> > Toll Free: 877-224-8987
> > Direct: 775-745-6404 (Outside the US and Canada)
> >
> >
> > -----Original Message-----
> > From: Aaron Pilcher [mailto:apilcher@itgcs.com <apilcher@itgcs.com> <
> apilcher@itgcs.com>]
> > Sent: Friday, April 14, 2006 4:54 AM
> > To: Brian Dennis; 'ZeroFlash'; 'Faryar Zabihi (fzabihi)'; 'James
> > Simons'; 'Cisco certification'
> > Subject: RE: OSPF route preferencing
> >
> >
> >
> > I 110% agree, but you could force a single ospf router to route over an
> > inter-area route when the ospf process would naturally select an
> > intra-area
> > route. I mean, making "unnatural" stuff happen is what PBR is all
> >
> > about.
> >
> >
> >
> >
> > -----Original Message-----
> > From: Brian Dennis
[mailto:bdennis@internetworkexpert.com<bdennis@internetworkexpert.com>
> <bdennis@internetworkexpert.com>
> > ]
> > Sent: Thursday, April 13, 2006 11:37 PM
> > To: Aaron Pilcher; ZeroFlash; Faryar Zabihi (fzabihi); James Simons;
> > Cisco
> > certification
> > Subject: RE: OSPF route preferencing
> >
> > To have inter-area routes preferred over intra-area routes, policy based
> > routing (PBR) will not work. PBR can not alter the route selection
> > process within OSPF itself. So this means that if the requirement is to
> > prefer inter-area over intra-area OSPF routes, PBR will not meet the
> > requirement.
> >
> > HTH,
> >
> > Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
> > bdennis@internetworkexpert.com
> >
> > Internetwork Expert, Inc.
> > http://www.InternetworkExpert.com
> > Toll Free: 877-224-8987
> > Direct: 775-745-6404 (Outside the US and Canada)
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com
[mailto:nobody@groupstudy.com<nobody@groupstudy.com>
> <nobody@groupstudy.com>]
> > On Behalf Of
> > Aaron Pilcher
> > Sent: Thursday, April 13, 2006 7:45 PM
> > To: 'ZeroFlash'; 'Faryar Zabihi (fzabihi)'; 'James Simons'; 'Cisco
> > certification'
> > Subject: RE: OSPF route preferencing
> >
> > To add to your points, PBR would also fit the bill.
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com
[mailto:nobody@groupstudy.com<nobody@groupstudy.com>
> <nobody@groupstudy.com>]
> > On Behalf Of
> > ZeroFlash
> > Sent: Thursday, April 13, 2006 9:27 PM
> > To: 'Faryar Zabihi (fzabihi)'; James Simons; Cisco certification
> > Subject: RE: OSPF route preferencing
> >
> > Creating a tunnel would certainly help in learning routes from one area
> > to
> > another to influence route selection based on inter/intra area routes.
> > The
> > only with this is to be careful not to learn your tunnel routes through
> > the
> > tunnel or you'll get recursive routing and the tunnels will bounce.
> >
> > I would also think about another type of tunnel, perhaps a virtual-link
> > here
> > might help.
> >
> > Just some thoughts off the top o the head.
> >
> > Later...
> >
> > ZeroFlash
> > -----Original Message-----
> > From: nobody@groupstudy.com
[mailto:nobody@groupstudy.com<nobody@groupstudy.com>
> <nobody@groupstudy.com>]
> > On Behalf Of
> > Faryar Zabihi (fzabihi)
> > Sent: Thursday, April 13, 2006 10:20 PM
> > To: James Simons; Cisco certification
> > Subject: RE: OSPF route preferencing
> >
> > As you might well know...AD will not work here. You might be able to
> > accomplish this through having another OSPF process but haven't tried.
> > You can also change routing protocol for those routes(but you probably
> > don't want that) Also if you want to get yourself into a mess read
> > this(I have and never implemented)
> > http://mirrors.isc.org/pub/www.watersprings.org/pub/id/draft-mirtorabi-o
> > spf-tunnel-adjacency-00.txt
> > I suggest you take a step back and see what the requirement really wants
> > you to do.
> >
> > Faryar Zabihi
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com
[mailto:nobody@groupstudy.com<nobody@groupstudy.com>
> <nobody@groupstudy.com>]
> > On Behalf Of
> > James Simons
> > Sent: Thursday, April 13, 2006 6:51 PM
> > To: Cisco certification
> > Subject: OSPF route preferencing
> >
> > Hello all,
> >
> > Another OSPF question for you all. OSPF always prefers intra-area
> > routes over inter-area routes, regardless of the route cost right? Is
> > there anyway to get a router to prefer an inter-area route? If there
> > are multiple methods, I would like to know as many of them as possible
> > since you never know what you will be allowed to do in the lab.
> >
> > thanks,
> >
> > Jimmy
> >
> > _______________________________________________________________________
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> >
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