From: Jonathan V Hays (jhays@jtan.com)
Date: Sun Jun 29 2003 - 12:05:52 GMT-3
Howard,
Thanks for the excellent exercise. I am quite familiar with the
manipulation and expected results of redistribution but it wasn't until
reading your questions that I realized I didn't understand the internal
mechanics and theory very well.
I'd like to make two corrections to your posts, if I may.
> You're making the assumption that all EIGRP routes have the same AD.
> Most are 95, some are 5, and some are 170.
1. The administrative distance for internal EIGRP is 90.
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/
fipr_c/ipcprt2/1cfindep.htm#36505
> >> Does EIGRP have more than one AD, as does IGRP?
2. From what I can know (at least in IOS 12.x) IGRP has only one AD,
100.
But after seeing your post, I wondered if I had missed something.
Admittedly I have ignored IGRP since last fall, when it was
unceremoniously ejected from the CCIE Lab, kicking and screaming.
I searched the 12.x documentation and found no reference to another AD
for IGRP. I also did some lab work, redistributing other protocols into
IGRP and so forth. The only AD I saw was 100. Am I missing something
here or was that maybe a typo in your post?
Thanks again. I'm still pondering your questions.
Jonathan
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf Of Howard C. Berkowitz
> Sent: Saturday, June 28, 2003 11:18 PM
> To: ccielab@groupstudy.com
> Subject: Re: protocol redistribution and route installation
>
>
> At 11:05 AM +0800 6/29/03, Punchi-san wrote:
> >Hi Howard,
> >
> >If OSPF is redistributed to EIGRP, can I say redistribution
> just import OSPF
> >routes into the EIGRP database. Those imported routes will
> be marked and
> >WILL NOT install in the local router regardless of the AD ?
>
> You're making the assumption that all EIGRP routes have the same AD.
> Most are 95, some are 5, and some are 170.
>
> At the CCIE level, you need to understand redistribution has the
> limits it does. There is a very good reason for what you are seeing.
> The hint I gave earlier: it's happening for the same reason ISIS and
> OSPF are designed to prefer intra-area over inter-area over external
> regardless of metric.
>
> Why do you think these clues are related?
>
> What could go wrong if an OSPF learned route were reported by EIGRP,
> and OSPF went down? What if RIP imported routes from EIGRP?
>
> Why don't iBGP routes get reannounced to other iBGP speakers in the
> same AS (ignoring special cases)?
>
> I'm hoping I can help you see the underlying general principles
> rather than just trying to memorize protocol A does this with
> protocol B.
>
> >
> >regards,
> >alec
> >----- Original Message -----
> >From: "Howard C. Berkowitz" <hcb@gettcomm.com>
> >To: <ccielab@groupstudy.com>
> >Sent: Sunday, June 29, 2003 3:18 AM
> >Subject: Re: protocol redistribution and route installation
> >
> >
> >> At 12:17 AM +0800 6/29/03, Punchi-san wrote:
> >> >Hi group,
> >> >
> >> >Just want to clarify the concept of protocol redistribution :
> >> >
> >> >R1 has both OSPF and EIGRP running and a route is
> originally learned from
> >> >OSPF. If I redistribute the route from OSPF to EIGRP,
> why the OSPF route
> >> >still get installed into the routing table. Isn't that
> the default
> >admin.
> >> >distance of EIGRP less than OSPF ? The route did
> install in the EIGRP
> >> >topoloy database. Any hints appreciated.
> >> >
> >> >thanks
> >> >punchi-san
> >> >
> >>
> >> Some hints: think about why OSPF and ISIS install
> intra-area before
> >> inter-area before external.
> >>
> >> Does EIGRP have more than one AD, as does IGRP?
> >>
> >> Why would it be important which protocol originally learned the
> >> route? What could go wrong if other protocols seemed
> authoritative
> >> for the same route learned by redistribution?
> >>
> >> While it's not the reason for this specific behavior, consider the
> >> purpose of split horizon. That should give you insight.
> >>
> >>
> >>
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