Slow network performance ...... 10/100 NIC set to 100 but when we change it to AUTO its like 5 times faster??? Why ???

[NICKel]

I have a friend who runs Quickbooks accounting software on a pretty fast network but copying files across to and from the server has been painfully slow .... My pal messed with alot of setttings and he adjusted the speed from 100 bps to AUTO ... and now the network seems quite a bit faster??? Does anyone know how are why this is?
thanks in advance .....

 

[nightowl]

What was your friends computer connected to? It sounds like he had a duplex mismatch. This happens when you have a device that is set to a specific speed and full duplex connected on the other end to a device that is set to auto detect. So, your best option is to leave both sides at auto detection or set both devices to a specific speed and duplex.

 

[NICKel]

Thanks for responding nightowl .. So your saying the duplex mismode?? Now I believe nothing was changed out of the box.... Shouldn't they be always set to auto? Seems like it would be the norm.

 

[spidey07]

both side of a link must be forced to speed/duplex. if only one side is forced the other side defaults to half-duplex mode - resulting in a "duplex mismatch".

this mismatch turns your network into mush...lucky to get more than a few Mbs out of it and its unbearibly slow.

best bet is to always leave all nics/switches set to auto.

 

[NICKel]

Anyone Know of any good sites where they show how to methodically troubleshoot why a network is running slow or weird?

 

[gunrunnerjohn]

You post the query here.

 

[NICKel]

Originally posted by: gunrunnerjohn
You post the query here.

Yes your right ! I always do !!! This place is wonderful for that! Like a great big extended family ! Thanks for all the feedback guys!

 

[Nevada]

Originally posted by: NICKel
Anyone Know of any good sites where they show how to methodically troubleshoot why a network is running slow or weird?

i would like to know this as well.

 

[spidey07]

Originally posted by: Nevada

Originally posted by: NICKel
Anyone Know of any good sites where they show how to methodically troubleshoot why a network is running slow or weird?

i would like to know this as well.

Unfortunately I think it just comes from experience. But whenever a LAN is running slow the very first thing to do is check for errors (CRC errors, runts, etc) and check speed/duplex on both end.

Cisco does have a pretty good sheet on troubleshooting ethernet somewhere.