Our office comprises of two buildings connected by fibber optics cable.Primary domain server is placed in one building and its backup domain server in the other.
total No. of nodes: upto 400
IP ranges: 192.168.41.1 to 192.168.41.254
192.168.42.1 to 192.168.42.254. These are created within the DHCP superscope.
Domain Server+DNS sever+DHCP server are all on same machine with WIndows 2003 Server Enteprise edition and their is no subdomian. This same machine is also the default gateway because after DHCP superscoping , Routing and remote access service has been turned On on it. Its address itself is in the IP range 192.168.41...
We are using this setup for almost 2 years and LAN was working fine till the beginning of this month. Now at random intervals of time, the PCs with the IP in range 192.168.41... don't communicate with the PCs in the other range i.e 192.168.42.... ; however they communicate well with the PCs within their same IP range and also ping the gateway.
We have tested by isolating different areas of LAN but no hardware problem was found.
What is the probable cause of this? Is this due to the use of USB devices for accessing internet?
Note that our PC users freely use USB devices and install any software on their PCs.