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Re: bandwidth aggregation between 2 hosts in the same subnet

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On 07/31/07 10:31, Ralf Gross wrote:
I've talked to one of the people of the network staff. He meant they
never used CEF in this type of scenario. I'm also not very familiar
with Cicso products.

My physical scenario is a Cisco 3640 router with two (10BaseT) ethernet connections connected to external ethernet to SDSL bridging modems. The SDSL modems bridge the ethernet to an ATM circuit. The ATM circuit is terminated in a Cisco 7206 (I think it's a 6) UBR router at my ISP.

Cisco Express Forwarding is being run on the local 3640 and the remote 7206 to control which connection the packets are being routed down. The local 3640 has two routes upstream, each being the remote IP for each of the ATM links. Correspondingly the 7206 has two routes to a (globally) routable subnet behind the local 3640.

As I understand it, CEF (ultimately) builds a forwarding information base (a.k.a. FIB) from the routing tables. So if you have multiple routes, CEF will know about them. CEF will then divide the traffic either "per flow" or "per packet" across all available routes so that more aggregate bandwidth is achieved.

In my scenario, I am using CEF via OSPF to combine two 1.1 Mbps SDSL connections to get close to 2 Mbps worth of aggregate bandwidth to the net. I can and do routinely receive 1.5 - 1.8 Mbps throughput via FTP / HTTP / BitTorrent. (Though BitTorrent by nature is not the best example)

If you could give me more details on your CEF setup, that would maybe
help me to show them what a CEF config should look like.

I think I have done so above. If you want config examples, contact me off list as I don't want to publish it to the world.

But I'm still not sure if CEF is a thing that is designed to work
with client-client connections.

I can't say for sure one way or the other. but It think that CEF will achieve what you are wanting to do as long as the device you are connecting to will support it. I know that more and more layer 3 devices support it. So, that being said if your switches are recent layer 3 switches, I'd say that they will support CEF. I don't know for sure though.



Grant. . . .
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