An ISP for one of my clients recently setup one of his dialup connection servers to use non-routable (gray) IP address in the reserved Class A 10.0.0.0 series. Is this acceptable practice?
The setup is a small network, 6 PC’s and one server. The server has Microsoft Small Business Server 4.5 (Proxy Server) loaded. Intermittently the PC’s would lose connection to the server and start broadcasting for a master browser reelection. These requests were logged in the server event log. We also found that sometimes the subnet masks of the PC’s would change from 255.255.255.0 to 255.0.0.0. The server acts as the DHCP server and the PC’s were using DHCP. Rebooting the server would fix the problem for a time, maybe 10 minutes, maybe a day. Sometime the problem would go away without rebooting the server. The network was 10.0.0.0 with subnet 255.255.255.0.
I found that the problem was caused by the dial-up networking connection to the ISP. One of the ISP’s servers is configured to use the Class A 10.0.0.0 addresses and network address translation the others use real IP addresses. The problem was intermittent because it would just depend on which of the ISP servers we happen to connect through. I resolved the problem by changing the internal network to 192.168.0.0.