backbone design

Unanswered Question
Jul 30th, 2007

We have 2 headoffices in the different cities.

In each city we have connections to Providers collocation where we have Cisco7206.

All 4 routers (Cisco7206) connected with each others via PLC.

We have a very critical and high bandwith traffic between HO's and planning to use load balancing.

i have few questions regarding that design.

1.all 4 routers will be in the same AS. Which routing protocol inside AS is better to use-BGP or OSPF?

2.regarding load balancing between Net1 and Net2.

How to do that load balancing is-1st path -link1-4-7 and 2nd path - link2-5-8.

3.which routing protocol to use at HO's routers?

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Overall Rating: 3 (1 ratings)
Amit Singh Mon, 07/30/2007 - 03:37

1. You can use any one of the routing protocol inside the AS. You can use EIGRP, OSPF and i-BGP for the requirement. As this topology is not big you can also think of Ibgp and making a fully mesh ibgp. But BGP and OSPF only supports equal-path load-balancing.Whereas if you are using EIGRP you can force it to use both the available path for equal and un-equal path load-balancing.

2. If you are using OSPf and EIGRP, you can simply use the network statement for the interface on which you want to run the routing protocol. Once the router will become adjacent they will learn all the routes from the neighor and depending on the routing protocol being used it can do both equal and un-equal path load-balancing.

Let us know if you have any questions.

-amit singh

rmv72 Mon, 07/30/2007 - 04:00

about fully mesh ibgp - i think it's not possible-because not all routers connected to each others. is't right?

Amit Singh Mon, 07/30/2007 - 04:18

Yeah, Correct, as they are not connected in a fully meshed design but still we can use BGP route-reflector configuration to run I-BGP. If all the routers are Cisco routers, then it would be nice to go with the EIGRP routing protocol. It should take care of traffic forwarding across all the available paths.


-amit singh

rmv72 Mon, 07/30/2007 - 04:35

Maybe it's not correct to use BGP route-reflector for 4 BGP routers?

All the routers are Cisco routers and as you adviced i'll use EIGRP.

Amit Singh Mon, 07/30/2007 - 04:46

Yeah, as its not a big topology so route reflector will not make much of sense here. You should be fine with EIGRP.

-amit singh

royalblues Mon, 07/30/2007 - 05:47


You do not require direction connection between the routers for IBGP.

Till the time you have connectivity to all the routers you can create a BGP full mesh.

You need route reflector only when you want to get away wth IBGP full mesh.

But as said above, i would be happy to use OSPF or EIGRP in your scenario


rmv72 Mon, 07/30/2007 - 21:08

Do you really think that i need to use iBGP instead of EIGRP in my example ( only 4 routers in the core)?

Can you tell me advantages of using iBGP?


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