From: ccie 2005 (cui666@gmail.com)
Date: Sat Jul 16 2005 - 14:02:18 GMT-3
Chris
Good explanation!
The other difficult part about redistribution I found in NMC DoiT labs
is to recognize which are core routing protocols, and which are edge
protocols, especially when they mingle together, for example
RIP<->OSPF<->EIGRP(assume they all are multi-points redistributions),
OSPF has to redistribute its external routes learned from EIGRP into
RIP and vice versa in order to play the core routing protocol
role(assume 0.0.0.0/0 is not allowed), the solution would be to use
route tags or prefix filters(route-maps and etc), I don't think
simply changing OSPF external routes' AD will work here...just my
$.02.
Regards,
Pat
On 7/16/05, Chris Lewis (chrlewis) <chrlewis@cisco.com> wrote:
> I'll try.....
>
> Start off thinking about an OSPF domain and an EIGRP domain connected at
> two points, say R1 and R2. Mutual redistribution occurs between OSPF and
> EIGRP at both points. Do you need to perform any filtering to stop route
> feedback? No, the reason is EIGRP has the concept of a separate
> administrative distance for external routes. If it did not have that, a
> route learned on R1 from OSPF would be fed in to EIGRP and from there
> EIGRP would tell R2 about the route with a lower administrative distance
> than OSPF, making R2 think that going back in to the EIGRP domian would
> be a better route than going towards the OSPF domain. Potentially the
> reverse operation could happen with the same OSPF route being learned on
> R2 and it telling R1 about it via EIGRP causing a loop.
>
> EIGRP never falls in to this trap because of the administrative distance
> of external routes being 170, so any EIGRP originated route will be
> preferred over a route redistributed in to OSPF on R1 and R2, as EIGRP
> has a lower internal administrative distance, likewise R1 and R2 will
> prefer any route learned from the OSPF domain over those redistributed
> in to EIGRP as the AD of 170 is higher than OSPF.
>
> If you consider an OSPF and RIP domain connected together, there is no
> default high AD for OSPF external routes to stop the route feedback
> happening. However, if you give OSPF externals an AD of say 180, it
> behaves the same as EIGRP and you don't need to filter between the two
> domains.
>
> Chris
>
> -----Original Message-----
> From: cacca mucca [mailto:caccamucca@hotmail.com]
> Sent: Friday, July 15, 2005 9:27 PM
> To: jjrinehart@hotmail.com; Chris Lewis (chrlewis);
> ccielab@groupstudy.com
> Subject: Re: LAB study guide
>
> Can you provide us with an example of the "distance ospf external to
> stop routes feeding back" ?
>
> Thanks
>
> >From: "Joe Rinehart" <jjrinehart@hotmail.com>
> >Reply-To: "Joe Rinehart" <jjrinehart@hotmail.com>
> >To: "Chris Lewis (chrlewis)" <chrlewis@cisco.com>,
> ><ccielab@groupstudy.com>
> >Subject: Re: LAB study guide
> >Date: Fri, 15 Jul 2005 08:45:08 -0700
> >
> >Agreed on the redistribution answers. There are several ways to answer
>
> >something, especially since the real test was whether or not ot
> >achieved the desired result.....
> >
> >----- Original Message -----
> >From: "Chris Lewis (chrlewis)" <chrlewis@cisco.com>
> >To: "Joe Rinehart" <jjrinehart@hotmail.com>; <ccielab@groupstudy.com>
> >Sent: Friday, July 15, 2005 8:38 AM
> >Subject: RE: LAB study guide
> >
> >
> >My opinion, FWIW is that they both have a lot of value to offer, DoiT
> >more for the routing scenarios, Internetworkexpert more for the
> >security and services side.
> >
> >I would add though that I often created simpler solutions to the NMC
> >answer keys, particularly regarding the redistribution scenarios. I
> >found it easier to use things like distance ospf external to stop
> >routes feeding back, rather than setting up lots of specific route
> filters.
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>
> >Joe Rinehart
> >Sent: Friday, July 15, 2005 10:27 AM
> >To: ccielab@groupstudy.com
> >Subject: Re: LAB study guide
> >
> >Well I used the DoIT lab workbook and had great results, what exactly
> >was out in left field? The thing that drove me crazy was
> >redistribution, DoIT would have at least three to four redistribution
> >points on each lab and you had to be really really careful about how
> >you filtered....
> >
> >Joe Rinehart
> >CCIE #14256, CCNP, CCDP
> >Data Network Consultant
> >AT&T Pacific Northwest Enterprise Markets
> >----- Original Message -----
> > > On 7/14/05, cacca mucca <caccamucca@hotmail.com> wrote:
> > > > I'm using the DOiT lab and it is out in the left field. I should
> > > > have
> >bought
> > > > the InterNetwork Expert. I even had an upgrade coming, but went
> > > > with
> >DOiT.
> > > > Kicking myself now.
> > > >
> > > > Just my 2 cents
> > > >
> > > > >From: "Hooman Parta" <hooman@voipsol.com>
> > > > >Reply-To: "Hooman Parta" <hooman@voipsol.com>
> > > > >To: <ccielab@groupstudy.com>
> > > > >Subject: LAB study guide
> > > > >Date: Thu, 14 Jul 2005 10:22:12 -0500
> > > > >
> > > > >Hi,
> > > > >
> > > > >I just started my LAB preparation and got my LAB already. Does
> > > > >any one recommend any of the LAB preparation materials. There are
>
> > > > >several
> >compaies
> > > > >with differnt options. NLI, IPEXPERT, IE, InterNetwork expert and
>
> > > > >much more.
> > > > >
> > > > >I know I should look for updated material which reflects the IPv6
>
> > > > >and
> >12.2T
> > > > >but which one do you think is better to start?
> > > > >
> > > > >Thanks,
> > > > >Hooman Parta
> > > > >
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