Subnet Mask Changes to Class A & B ... but still has access to the network??? (Baffled)

I'm running Win 98 SE w/s and Intel 10/100+ NIC's

We're using the standard internal IP scheme (192.168.???.???). We have 5 Gateway PC's that change the subnet mask on their own, putting the SNM into a totally different class, but they still have access to the network, etc

Example

Day 1: IP = 192.168.100.10
SNM = 255.255.255.
DG = 192.168.100.

Day 2: IP = 192.168.100.10
SNM = 255.255.0.0 (changed
DG = 192.168.100.

Day 3: IP = 192.168.100.10
SNM = 255.0.0.0 (changed again
DG = 192.168.100.

Day 4: Run WINIPCFG - Release All / Renew Al

Result: IP = 192.168.100.10
SNM = 255.255.255.
DG = 192.168.100.

Process repeats itself, but the access to network resources, Internet, e-mail is unaffected

I'm trying to figure out where this problem is occurring, i.e. Registry setting, NI

If anyone has seen this, or knows of a fix, please advise. I would greatly appreciate it

Ken in Pgh, PA