From: John (jgarrison1@austin.rr.com)
Date: Tue Mar 04 2008 - 18:48:14 ARST
Well at least it makes sense to you. I'll try again tommorow and then I'm
gonna try something else if I can't get it to work
----- Original Message -----
From: "Scott Vermillion" <scott_ccie_list@it-ag.com>
To: "'Sadiq Yakasai'" <sadiqtanko@gmail.com>; "'Timothy Chin'"
<Tim@1c-solutions.com>
Cc: "'John'" <jgarrison1@austin.rr.com>; "'Hash Aminu'" <hashng@gmail.com>;
"'Carlos Alberto Trujillo Jimenez'" <carlos.trujillo.jimenez@gmail.com>;
<ccielab@groupstudy.com>
Sent: Tuesday, March 04, 2008 2:16 PM
Subject: RE: redistribution
> Yep, it makes perfect sense Sadiq! And I believe if you follow the IE
> solution to OSPF/EIGRP mutual redistribution, this distance 109 thing is
> likely required. Most found trouble with the solution as give, though,
> and
> wound up doing something different (such as tagging and filtering at the
> OSPF/EIGRP seam so that this isn't an issue). I obviously don't recall
> all
> of the details, but in reviewing quickly the postings on the IE forums,
> the
> solution as given fails when a backup link is active. Hence the
> alternative
> approaches that a good many of us wound up implementing before moving on
> to
> the remainder of this lab.
>
> IIRC, the solution given was meant to stretch our minds and show us a way
> of
> using distance in wacky ways to solve loops that result from massive
> mutual
> redistribution of practically everything everywhere. But in the end, it's
> not a very good approach and, as I said, actually fails when you bring up
> the backup link...
>
>
> -----Original Message-----
> From: Sadiq Yakasai [mailto:sadiqtanko@gmail.com]
> Sent: Tuesday, March 04, 2008 1:06 PM
> To: Timothy Chin
> Cc: John; Scott Vermillion; Hash Aminu; Carlos Alberto Trujillo Jimenez;
> ccielab@groupstudy.com
> Subject: Re: redistribution
>
> Guys,
>
> I have checked the lab and this comes back to what I said ealier:
>
> You are redistributing RIP into OSPF on SW1.
>
> Then you are mutually redistributing OSPF and EIGRP on three points;
> R2, R3, R4. Now, the rip routes you have redistributed into OSPF on
> SW1 go into OSPF and then;
>
> 1. on R2: they enter EIGRP and then come back into OSPF on R3 as
> externals. These LSAs would get sent everywhere and even down to SW1
> again (where they originally got redistributed into OSPF). SW1 would
> gladly put these routes into the routing table. Why? Because they
> would have a lower AD (OSPF 110) than the original prefixes (in RIP
> with AD of 120) and they would appear to have originated from EIGRP
> (which is false). This would now make these prefixes unreachable in
> the whole network because the originator of these prefixes into the
> OSPF no longer has the correct ones.
>
> 2. similar behaviour could be seen on R3, when the routes enter into
> EIGRP in R4 and come back into OSPF on R3 and these now get sent back
> to SW1.
>
> Now to mitigate this problem, you simply set the AD of RIP routes to
> 109 on SW1 so that no matter what, these prefixes will never be
> accepted on SW1 from OSPF even after they ahve gone through the EIGRP
> domain.
>
> Do you guys see the point?
>
> HTH
>
> Sadiq
>
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