We have been having a very strange problem affecting a lot of users within our company and we are struggling to understand the underlying issue.
Briefly, we have a range of switches (but mainly 2950's and 3750's) with various levels of IOS located in the UK. We are getting consisent reports of slow responses when people log in using windows which seems to be the roaming profile being downloaded from the local DC.
On further investigation we have found that the DC's (mainly Windows 2003) are erroring on the port with a large amount of Input and CRC errors. However once we reset the port (either shut/no shut) or a physical pull of the cable then the errors disappear and all is ok.
The monitoring we have shows no real problems beforehand and no correlation between these problems. The other thing is that this is a mixture of machines and network cards , Dell/HP/Broadcom etc.
We are stuck by this and we can not understand any correlation or single issue causing this.
For servers we hard code to port speed of server.