From: Arifur Rahman (arahman@cisco.com)
Date: Sun Sep 28 2003 - 15:01:17 GMT-3
Hi
I have a question here - if there is no routing loop due to distance or for
some other reason then do I still need to filter out prefix? For example
r1
/\
/ \
r2--r3--lo0
r2-r3 link is running ospf and r1-r2, r1-r3 eigrp. Due to redistribution r2
will get lo0 from both ospf and eigrp. Distance will be 110 and 170
respectively. So r2 will ospf. Do I still need to use any kind of filter here?
thank you - Arif
At 10:20 AM 9/28/2003 -0400, Jonathan V Hays wrote:
>The "distance" command is good for fault tolerance and it is good for
>forcing the router to prefer the native routing protocol. But it may not
>prevent routing loops, depending on the network topology. Even with the
>distance command working properly you may still have to filter with
>distribution lists or route-maps.
>
>In the ASCII diagram below, we can suppose that mutual redistribution
>between different routing protocols is taking place on R2 and R3, and
>perhaps R4 also. Using "distance" to force each router to prefer its
>native routing protocol in the routing table is still not going to stop
>routes from being forwarded in a loop.
>
>
> R1
> /\
> / \
>R2--R3
> \ /
> \/
> R4
>
>I think the thing to learn is that when it comes to redistribution on
>the CCIE Lab exam, you cannot simply memorize a technique and use it
>every time. Each situation is different.
>
>Jonathan
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>navaid@rogers.com
>Sent: Sunday, September 28, 2003 9:45 AM
>To: info@mpauli.de; chipn@intraworx.net
>Cc: ccielab@groupstudy.com
>Subject: Re: Re-3: Mutual redistribution.
>
>
>Marcus,
>Thanks for reply.
>
>I think "distance 120 150.100.1.253 0.0.0.0 10" will help me with RIP
>and OSPF. What about EIGRP ?
>
>Another question is that: Do I need to do this even if there is only one
>redistribution point.
>
>Thanks,
>
>Navaid
>
> >
> > From: info@mpauli.de
> > Date: 2003/09/28 Sun AM 08:46:16 EDT
> > To: navaid@rogers.com,
> > chipn@intraworx.net
> > CC: ccielab@groupstudy.com
> > Subject: Re-3: Mutual redistribution.
> >
> > Hi Navid,
> >
> > well I'm not using this technique via route-map but via distance, here
>is an example:
> >
> > router rip
> > version 2
> > passive-interface Serial0/0
> > passive-interface TokenRing0/0
> > passive-interface Loopback0
> > network 133.10.0.0
> > network 150.100.0.0
> > neighbor 150.100.1.253
> > distance 255
> > distance 120 150.100.1.253 0.0.0.0 10
> > distance 120 150.100.1.254 0.0.0.0 20
> > !
> > access-list 10 remark Permit only 192.177.ODD].0/24
> > access-list 10 permit 192.177.1.0 0.0.254.255
> > access-list 10 permit 10.0.0.0 0.255.255.255
> > access-list 20 remark Permit only 192.177.[EVEN].0/24
> > access-list 20 permit 192.177.0.0 0.0.254.255
> > access-list 20 permit 10.0.0.0 0.255.255.255
> >
> > Hope I could help...
> >
> > Cheers
> > Marcus
> >
> >
> > -------- Original Message --------
> > Subject: Re: Re: Mutual redistribution. (28-Sep-2003 14:30)
> > From: navaid@rogers.com
> > To: cbsnow31@yahoo.com
> >
> > > Chris,
> > > you suggested to use route-map to drop AD. Where this route-map will
>be
> > > applied ?
> > >
> > > Navaid.
> > >
> > > >
> > > > From: christopher snow <cbsnow31@yahoo.com>
> > > > Date: 2003/09/28 Sun AM 07:12:02 EDT
> > > > To: chipn@intraworx.net
> > > > CC: ccielab@groupstudy.com
> > > > Subject: Re: Mutual redistribution.
> > > >
> > > > Doyle covers this in TCP/IP Vol I very well in the
> > > > redistribution section. I have adopted his method and
> > > > it works every time. He uses the distance command and
> > > > sets both protocols above their normal distance...
> > > > i.e. if you were doing EIGRP and OSPF set both
> > > > protocols at 130. Then use route maps to drop the
> > > > selected routes back to their normal distance within
> > > > each protocol. This prevents route feedback and
> > > > establishes redundancy if you have more than one point
> > > > of redistribution.
> > > >
> > > > HTH
> > > >
> > > > Chris Snow
> > > >
> > > > --- chipn@intraworx.net wrote:
> > > > > I'm looking for opinion on lab strategy.
> > > > >
> > > > > If you encounter a mutual redistribution scenario
> > > > > with multiple
> > > > > redistributions points on the lab, would it be in
> > > > > your best interest to
> > > > > explictly control your routing information to
> > > > > prevent route feedback? It
> > > > > is possible to have complete connectivity in this
> > > > > scenario without
> > > > > filtering, but still have the potential for routing
> > > > > loops.
> > > > >
> > > > > I thought this would be the best place to get some
> > > > > expert advice on the
> > > > > subject.
> > > > >
> > > > > Thanks.
> > > > >
> > > > > ***Get your CCIE and a FREE vacation:
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> >
> > To: navaid@rogers.com
> > chipn@intraworx.net
> > Cc: ccielab@groupstudy.com
> >
> >
>
>1
>
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