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Switch seems to be slow.

Posted on 2004-08-27
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I had to shut down all our company servers and unplug the switches early this week in order to have a generator installed in our company.  The switches were all unplugged.  

Since then we had some network problems and today I finally figured out that any computer that is plugged into one switch is having slight network problems.  It is a Cisco Catalyst 2950.  Anyone plugged into that switch is a little bit slow.  I can easily tell by coping one file down to their computer.  This should take about 5 seconds to do and anyone plugged into that switch will take 5-7 minutes to copy this file.

My question is, do I assume the switch just went bad after being unplugged and then plugged back in?  Is there anything I can test for?

Thanks,
Lori
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Question by:LATurk
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by:mikebernhardt
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Check for any duplex mismatches including on the uplink port. And it may not be that switch- it could be the other end of the uplink. If a change wasn't written to NVRAM then the switch would have reverted to an older config on reboot.
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by:LATurk
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I checked both ends of the uplink and they are both set to 100/full.
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by:mikebernhardt
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Have you tried copying the same file from one server to another on the same switch? That would tell you if it really is the switch or something else upstream.

Check if the servers and switch ports are set to "auto."
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by:LATurk
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Actually, there are no servers plugged into the problem switch.  The server switch seems to be be fine - there are a few office computers that are plugged into the same switch as the servers and they are working fine.

I did look at one of the servers that is the Main Domain controller.  It's NIC card is set to 'Hardware Default'.  Since the switch is set to Full, shouldn't the card be set to Full also?
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by:mikebernhardt
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What I meant was, try transferring a file between 2 computers on the problem switch and see how it goes. If it seems OK, do the same thing between one of those PCs and something upstream, using the same transfer method (file sharing or whatever) and compare times.
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by:LATurk
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It works fine when I copy from one computer on the problem switch to another computer on the problem switch.
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by:mikebernhardt
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Then the switch itself isn't the issue. What kind of uplink do you have from that switch and to what does it connect? Can you do the same thing from a PC on the suspect switch to something on the upstream switch? Does it connect to a router or what? Are all of your PCs and servers on the same IP subnet or is there a router in between?
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by:mikebernhardt
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An explanation of your toplogy would be helpful at this point. Also, try to determine: is ALL traffic from the problem area slow, or just some things? To where is it bad and where is it OK? That's where I'm going.
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by:LATurk
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one other odd thing I noticed was if I try to copy this file(39,800 kb) from one folder on one of our servers to another folder on this same server, it takes long.

If I copy this file from my computer up to this server, it goes quick.

This server is not plugged into the problem switch. I am plugged into the problem switch.

When I go to a computer that is NOT on the problem switch and do the same thing, it works fine.
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by:LATurk
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Thank for your help so far.  I am going home now - it's after 5 here.  I'm going to come in tomorrow and I will check into your last two responses.  It will be easier to figure this out with no one in the office.
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by:mikebernhardt
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I'm not sure I understand. Do you mean that you are sharing a drive on a server, and if you initiate a copy from one folder to another on the server, it goes slow- but if you just copy from your own machine to the server it is OK?

Try a speed test from the internet from a PC on that switch and from one that isn't, at http://speedtest.dslreports.com

See if the speeds are approximately the same, or way different.
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by:LATurk
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Question: I'm not sure I understand. Do you mean that you are sharing a drive on a server, and if you initiate a copy from one folder to another on the server, it goes slow- but if you just copy from your own machine to the server it is OK?

Answer:  Yes - you understand correctly.

I did the speed tests from a computer on the problem switch and a computer on a good switch:

Problem Switch:  Download speed:  711944 bps, or 695 kbps.
                        Upload speed:  1195476 bps, or 1167 kbps.

Good Switch:  Download speed:  402087 bps, or 392 kbps.
                     Upload speed:  550214 bps, or 537 kbps.


 
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by:lrmoore
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>Main Domain controller.  It's NIC card is set to 'Hardware Default'.  Since the switch is set to Full, shouldn't the card be set to Full also?
ABSOLUTELY! Both NIC and switchport must match.

>It is a Cisco Catalyst 2950.  Anyone plugged into that switch is a little bit slow.
>This server is not plugged into the problem switch.
Have you verified the integrity of the uplink cable, speed, duplex settings between these two switches? Is there one and only one uplink, or multiple uplinks? Can you look at the interface statistics on the 2950 and look for error conditions, especially CRC errors and collisions on any one port?

Are appearances deceiving? "problem" switch has better performance statistics than the "good" switch? It appears that the "problem" switch is almost 2x as effecient as the "good" switch.

Problem Switch:  Download speed:  711944 bps, or 695 kbps. <===
Good Switch:      Download speed:  402087 bps, or 392 kbps. <----

Problem Switch:   Upload speed:  1195476 bps, or 1167 kbps. <===
Good Switch:        Upload speed:  550214 bps, or 537 kbps.  <----

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by:LATurk
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>I checked all our servers and made sure the Nic cards and the switch ports were both set to 100/full.  They now are.

>We have 5 Cisco Switches.  Switch 1, 2, 3 and 4 are all plugged into switch 5.  I verified both ports of the uplink cable on the problem switch and they are both set to 100/full.

>The speed test does confuse me.  My computer which is plugged into the problem switch does better than the computer on a good switch.

I just ran the test one more time and the results are the same but much closer.
Problem Switch: Download: 351, Upload: 1155
Good Switch:     Download: 269, Upload: 895

I am not a network or a switch pro.  I have a "pro" that comes in when we have problems that are over my head.  I'm hoping he can stop in on Monday because I think I am at that point. I am not sure how to check the interface statistics for error conditions.  I did notice though that there were "Late Collisions" (98) showing up on my port.  Only a few ports on that switch showed any Collisions.  I will check a computer that has 0 collisions and let you know if it is experiencing any of the slowness.

Thanks!
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by:lrmoore
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Any collisions on a switchport indicates a possible duplex mismatch.
The station reporting the late collision is merely indicating the problem; it is generally not the cause of the problem

"sho interface" on the switch will reveal all the error counts.

Good reference doc:
http://www.cisco.com/en/US/products/hw/switches/ps607/products_installation_and_configuration_guide_chapter09186a008007d9a3.html
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mikebernhardt earned 500 total points
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If everything is set to full duplex and you saw collisions, then something was wrong. It sounds like you may have made a couple of changes in duplex settings. Your problem switch seems to be performing as at least as well as the good switch, so I think that rules out the switch hardware as a problem.

I have seen many cases where setting the server and switch ports to "auto" worked a lot better than hard setting them to 100/full duplex, even though they negotiate to 100/full duplex. In other cases (especially older NICs) the opposite is true.

I suspect your server hardware configuration is, or was, the problem.
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by:fatlad
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Late collisions are often simtomatic of cable runs that are too long or of high electromagnetic interference, the uplink cable does not happen to run near heavy machinery does it? Like a sparkling new generator perhaps?

FatLad
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by:LATurk
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No - Just the wiring was done for the generator.  The actual generator has not been installed yet.

Our 'network pro' is coming in tonight.  We recently upgraded the last of our NT servers and switched over to Native Mode.  I'm wondering if something got messed up when the servers were restarted.  I also sent the current switch configuration info for all our switches to our 'switch pro' to see if anything went back to default when the switches were turned off - on.

One the 'problem switch' - I check all the computer nics and the switch ports and now all are set to 100/Full.  That made no difference. And the slowness still only appears for computers plugged into this one switch.

I will update this question after tonight.
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by:fatlad
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I suspect it is due to the uplink, either the cable has been damaged or something is causing interference. There is a possiblity that another machine's nic card is causing the problem, by creating late collisions but that is going to take a massive amont of troubleshooting.
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by:LATurk
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Our 'switch pro' came in.  He went through everything and was really stumped as to what the problem was.  

The last thing he tried was upgrading the firmware on the problem switch and that solved the problem.  

It's odd though because 2 other switches that are the same model were using the same older version of firmware with no problems at all.

It is also odd the switches were all shut down about 10 months ago when we moved to a new office.  We had no problems at that time after turning them back on.  

Thanks for all your help!
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