Forcing EIGRP to take different path to border routers - problem?

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Jun 2nd, 2008
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Hi,


I have this routing problem and need some help please.


two 6509 switches as core switches in the datacenter runing 255 vlans. have hsrp between them. due to some L2 issues our L2 designer at the last momenet revert all on VLAN1 on one of the 2 6506 core routers. so, all traffic from the datacenter gets to vlan1 (L3) interface on core router 6506 1.


there are two core routers connected via two vertical links to two border routers (no cross links between the core routers and border routers due to lack of facility on the MUX connecting these core routers to border routers).


Now, trffic on core 1 router, always reaches border 1 router and out to the Internet using our first BGP border routers and to the provider. naturally EIGRP sees two hops and higher cost and wont send traffic to core router 2 which is connected via a vertical connection to my border 2 router and no traffic flows out my second border router using BGP to our second provider?


Traffic comes in though but nothing flows out!?


I was thinking to split my IP block on core 1 router and put static route pointing to core 2 router and while there it knows how to get to border 2 and out our second border oruter out.


is this idea something that might work?

is there any other ways to do this, say by varying the EIGRP parameters and force traffic the other way, some of the traffic at least?


One more qquestion which might sound sily?: do I need to define all the IP blocks (networks) that I hav edefined for BGP on my border routers for EIGRP between the core routers (s of them) and the border routers (2 of them)?



Please advise.


Regards,


Masood



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Amit Singh Mon, 06/02/2008 - 19:22
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  • Cisco Employee,

Masood, It would be really nice to a network topology diagram for this.


-amit singh

m-abooali Tue, 06/03/2008 - 17:05
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Hi Amit.


Thanks for responding.


a diagram is attached and also sho ip eigrp 1 nei out put on all 4 routers are also attached.


I think I need to add the other two public IP blocks to the eigrp 1 network statements. 198.x.x.0 block is used for connectivity between devices.


if you look at the IP blocks being advertised in BGP to two providers, you see tha they have not shown in the sh ip eigrp 1 nei output on the core routers.


Please see the text file for eigrp 1 configuration on 4 routers and also the output of the sh nei command.


I need to have traffic go out the seconf ISP link gi 5/1 through border 2. currently all goes out through border 1 since the cost is lower than the one for border 2 but there must be a way to force that traffic just some of them to go out to router border 2.


Please advise.



Regards,


Masood




m-abooali Wed, 06/11/2008 - 08:44
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Hi Amit,


I have posted the netwrok topology and been waiting on your take on this issue. I did post a fresh one linking it to this posting.


Please see if you can help me given the topology provided.


I beleive, if I make some adjustment to make the path (two hop to border 2 router from core 1 to core 2 and to bordr 2) to have same cost as core 1 to border 1, then traffic must split!?


Please advise.


Thx,


Masood


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