RE: Interesting BGP/EIGRP interaction

From: Joseph Brunner (joe@affirmedsystems.com)
Date: Sun Jul 06 2008 - 14:49:36 ART

my original post had both router's routing table; neither was bgp

Router "NYCORPHQ1" with beter eigrp metric on the "redistribute bgp 65000"
had them as static to null0 (so I can keep advertising always to bgp)

S 66.55.5.0/25 is directly connected, Null0

S 66.55.5.128/25 is directly connected, Null0

While router "NYCORPHQ2" with worse eigrp metric on the "redistribute bgp
65000" command had them VIA EIGRP towards NYCORPHQ!

D EX 66.55.5.0/25 [170/307200] via 10.10.10.1, 00:06:35, Ethernet0/1

D EX 66.55.5.128/25 [170/307200] via 10.10.10.1, 00:06:35, Ethernet0/1

When I took Luan's great advise and routed them towards NULL0 with an AD of
54 (instead of the previous 254), this of course beats eigrp and I had the
routes known via static to null with ad 54 on both routers- BUT
THEY WERE BEING SENT OUT TUNNELS ON EIGRP!

AMAZING...

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Shawn Zandi
Sent: Sunday, July 06, 2008 6:41 AM
To: Joseph Brunner
Cc: Luan Nguyen; Cisco certification
Subject: Re: Interesting BGP/EIGRP interaction

Joe,
Definitely it use IP routing table not BGP table, for redistribution fpr the
sake of "AD",
I don't see any problem here, before "Redistribution" maybe you have those
routes as "BGP" entries in your routing table, EIGRP using Static-to-Null,
is just over-writing those routes in your routing table with D instead of B
cause static AD is preferred (If I understood the situation correctly...)
whats your routing table before redistribution? 

-- 
Sincerely,
Shawn Zandi
Routing, Switching & Security Consultant
CCIE (Routing & Switching) - MCSE

eLINEAR SOLUTIONS ME FZ LLC
Dubai Internet City - Building 13
web: http://www.shafagh.com
email: shafagh@shafagh.com
Fax: +971 4 390 8548

On Sun, Jul 6, 2008 at 1:02 PM, Joseph Brunner <joe@affirmedsystems.com>
wrote:

> Right, but the redistribute command is supposed to take routes from the IP
> routing table
>
>
>
> see
>
>
http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_pi1.html#w
>
p1015390<http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_p
i1.html#wp1015390>
>
>
>
> Where the doc cd states "The following example configures BGP routes to be
> redistributed"
>
> Wouldn't bgp ROUTES mean ROUTES known via BGP in the current IP routing
> table (FIB)
>
> not just any information (including rib failures) in the bgp table.
>
>
>
> Tony Li/Yakhov Rekhter where are you when we need you!
>
>
>
> Thanks,
>
>
>
> Joe
>
>  _____
>
> From: Luan Nguyen [mailto:luan.m.nguyen@gmail.com]
> Sent: Sunday, July 06, 2008 1:05 AM
> To: Joseph Brunner
> Cc: Cisco certification
> Subject: Re: Interesting BGP/EIGRP interaction
>
>
>
> Joe,
> After researching, that is the correct behavior.  BGP local-rib is used to
> export routes.  The routing table is the forward information base, which
> routes are installed using best-path algorithm.
> Routing Protocols----->Import Policies--->Route Information Base
> (RIB)--->export policies---->routing protocols
>
> |
>                                                                    Route
> Selection
>                                                         Forwarding
> Information Base (FIB)
>
> For example, when you have a rib-failure that means the FIB has a better
> route then the route come from BGP local-rib.
>
> -Luan

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