The school called me because the back half of the campus lost connectivity to the network and was unable to obtain IP addresses. The computers in the back half are all connected through a single switch. The school said that all the computers that lost connectivity were connected through a single 10/100 switch, and I suggested they purchase a new one. They got a new 10/100 switch and it appears to have the same problem.
When I got there, I unplugged all of the network cables from the switch and plugged in only the WAN cable. Then I plugged in one cable at a time. With 2 or 3 computers connected, they were able to obtain IP's and go on the internet. If I plugged another cable connected to a PC into the switch, the 2 or 3 computers that had connectivity suddenly lost it. Attempts to go to a website or refresh the IP fail.
I'm wondering, is it possible that the switch is overloaded? Is it possible the Windows 2003 Server (DHCP and DNS server) is running out of IP addresses (there are less than 100 PCs at the school)? Is the new 10/100 switch incompatible with the Gigabit switch by the T1? What could this be?
I'm attaching a diagram of the school's network setup and the problem area. Any suggestions ?