For the past couple of days I have had users complaining they cannot access the internet or access SQL(using SAGE 200 Accounting). Upon further investigation I find that the machines in question is very slow in resolving DNS names. Pinging by IP Address returns an anwser straight away; whereas on specific servers (eg SQL Server and the Domain Controller/DNS Server) I ping by it's name and nothing happens for around 5/10 seconds then it returns a healthy ping <1ms no dropped packets. Thats led me to believe that the slowness in name resolution has resulted in people not able to access the internet and get SQL error msg under SAGE (Bizzarely Outlook connected to Exchange still works ok). Now the way to get the machine working is either to:
1) Repair the Connection under XP
2) Plug the PC into a different switch port/another switch (they are a mixture of 100/1000mbits Layer 2)
3) Unplug the Cat5 Patch lead and change the physical CAT5 Port
4) Reboot whatever switch the PC(s) are plugged into.
This cures the issue for a few minutes then it will return, also of note:
1) It always happens to the same group of PCs (intermittently; not always at the same time)
2) I have rebooted both Domain Controllers (also DNS Servers themselves: Windows 2000 Server SP4) There is no notable DNS issues in Event Viewer..same with PCs..no Event ID of note. They are all running Windows XP SP2 by the way
Things I will try:
There is a central switch that all the servers are attached to. this is a 24port Gigabit switch that all other switches attach to. I have rebooted all of this and I have ordered a new 3Com 24 Port Switch to replace it just in case this week.
I will also hire a Network Meter to test all the cabling to ensure the horizontal cabling is not damaged (if it was a Switch or DNS Server issue surely it will effect all the PCs the network other then just a fixed group of them I mentioned before ?
Any other troubleshooting I should try ? (sorry about the long winded explaination!)