Throughput of 2960-48TT.

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Oct 13th, 2009
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Hi all,

I'v a question related to throughput of 2960-48TT. We have hub (3560G) and spoke (2960-48TT,...and so on) LAN topology.

One spoke switch, 2960-48TT, connects all our servers. All of them are with GEth cards connectted to FEth ports of spoke switch. And now problem: from time to time we observe that we cannot copy files from\to...server to client in speed reasonable speed. Speed is evidently slower.

How to resolve this issue?

Any idea?



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Joseph W. Doherty Tue, 10/13/2009 - 04:25
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How slow is slow?

From what you've defined, your two most likely bottlenecks are the 100 Mbps connections to the servers and single(?) gig link between server switch and 3560G.

A 2960-48 has a 32 Gbps fabric and 10.1 Mpps (i.e. should support wire rate for all its ports).

Leo Laohoo Tue, 10/13/2009 - 13:17
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It's always a network fault. If the servers were mis-configured or the cluster has failed or some files get corrupted it's always a network fault. It's always easy for the server team to look at their very crude "diagnostics" tool and point the (dirty) finger at networks issue.

Look at the link utilization of the ports to/from the servers, look for any potential problems, speed/duplex mismatch or line errors, etc. If your switch has been working without a hitch since the day you've put it on then most likely the servers are acting up.

pnicolette Wed, 10/14/2009 - 10:50
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As was mentioned, first check the 2960 port counters for errors, and make sure none are running half-duplex. (Our servers and switchports are set to auto speed & duplex.)

If you still have problems, consider finding the busiest server(s) and patching them directly to your 3560G so you can benefit from their Gig NICs and lighten the load on the server spoke link. We keep our servers near the hub switch (and stack 3750 hub switches if necessary) to make this easier.

Also, look for output drops (more than a few) on "Show interface" at both ends of the server spoke link to see if it's oversubscribed. If so, and you don't already run multiple gig links (Etherchannel) between server spoke switch and hub, consider it.

glen.grant Mon, 10/19/2009 - 13:16
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If the uplinks are the bottleneck you can try using a etherchannel up to the 3560. When its slow get on the 2960 and use the "show controllers utilization" command and it will tell you where the problem is as it will give port utilization rates of all ports along with the switch fabric utilization . That command will also work on your 3560.


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