Can't get gigabit speed on switch 3560.

Unanswered Question

Hi all.

Im using Cisco 3650 24p/48p with SFP between the switches. I have made some large file transfer (4Gb HD avi's : )) just to see what kind of speed im getting. Im using Cacti to mesure the interfaces.

I'm astound that i seldom get over 100Mbs (megabits) witch i easily should get.

I used different clients and servers, checked that the interfaces are on GB witch they all are.

Can't find out whats wrong! Greatful for all help.


I have this problem too.
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andrew.butterworth Wed, 10/29/2008 - 13:24

Copying files is not generally a good way to determine throughput due to OS & protocol limitations. I assume these are 3560G's with hosts connected at 1Gbps and not standard 10/100 3560's......

I would make a baseline using just a cable between the two hosts and perform the file transfer to see what speed you achieve. Once you have this you should perform your testing again and compare the results. If it is wildly different then it's possible you are having a problem.

There are known issues if you have QoS enabled (CSCsc96037) so that could be what you are hitting, however I would still perform the baseline as I suggest and go from there.



Willem de Groot Wed, 10/29/2008 - 23:36


I use iperf.exe to generate traffic and to messure the speed.

It tries to send UDP or TCP as fast as possible.

Its a great small .exe, freeware a beleave.

As noted, first do a speed-test with crossover-cable (can be a normal cable with Gb interfaces).

Note that Windows-clients TCP/IP stacks can't send at 1 Gb. Vista seems to get up to 600Mb, but never 1Gb!

Also be aware of Virusscanners, these can reduce your traffic extremly as well.

Also note that Gb-SFP send at a fix rate. If they function, they will work at 1Gb, if not, you will have Interface errors.



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