RE: OSPF, EIGRP redistribution

From: Kenneth Wygand (KWygand@customonline.com)
Date: Sun Jan 25 2004 - 02:10:09 GMT-3


Alsontra,
 
I don't understand what you mean when you say "As I understand it, this
configuration causes either R6 or R2 to become an ASBR and that ASBR then
advertises all routes learned from SW1. Which puts you in situation that
causes less than optimal routing on R6 or R2." The configuration you have listed simply prevents loops from a potential "chained" redistribution. It just "tags" routes so once they pass through one distribution, they will not be redistributed back to the original protocol.
 
Can you please explain further, and let us know what routing protocols are running on which routers?
 
Thanks!
Ken

        -----Original Message-----
        From: nobody@groupstudy.com on behalf of alsontra@hotmail.com
        Sent: Sat 1/24/2004 8:36 PM
        To: ccielab@groupstudy.com
        Cc:
        Subject: OSPF, EIGRP redistribution
        
        

        ****Let me start by saying I've read about 100 posts on this subject, but I
        haven't found a definitive answer. ****
        
        I am working on scenario that involves mutual distribution of OSPF and EIGRP
        using route maps. The topology looks something like this:
        
        
        --------R5--------
        | |
        R6 R2
        | |
        -------SW1------
        
        Using the following route maps on R2 and R6:
        
        <snip>
        route-map OSPF-TO-EIGRP deny 10
         match tag 111
        !
        route-map OSPF-TO-EIGRP permit 20
         set tag 90
        !
        route-map EIGRP-TO-OSPF deny 10
         match tag 90
        !
        route-map EIGRP-TO-OSPF permit 20
         set tag 111
        !
        </snip>
        
        R6 and R2 are doing mutual distribution using route-maps and all is well
        until I advertise any networks connected to SW1. As I understand it, this
        configuration causes either R6 or R2 to become an ASBR and that ASBR then
        advertises all routes learned from SW1. Which puts you in situation that
        causes less than optimal routing on R6 or R2.
        
        Is it possible to use "just" route tagging in a mutual OSPF-EIGRP
        retribution situation and avoid less that optimal routing? I know from
        previous posts that I can use the distance command in the following fashion
        to elevate the situation. <see below> However, is route tagging alone
        capable of solving mutual distribution scenarios without causing less than
        optimal routing? Or is it just possible that I've misconfigured something
        somewhere, and that's the cause of the less that optimal routing?
        
        access-list 10 permit <networks>
        
        access-list 10 permit <networks>
        
        and applying it under router OSPF:
        
        router ospf 100
        
        distance 171 <neighbors address> 255.255.255.255 10
        
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