I am using the "Single Static IP" feature of my Westell DSL Router to expose one of the computers in my network to the Internet. This has worked fine for 4 months. I am using DHCP on all 5 computers in the network. The others get an IP address from the private LAN range (22.214.171.124 - 126.96.36.199), while this server gets the external IP address, which is whatever the Verizon DHCP server assigns to my router. Since today, the exposed computer's DHCP lease is only good for 5 minutes and after that it cannot renegotiate a lease and switches to a static IP address. Here is the error in the Windows XP event log:
Your computer was not able to renew its address from the network (from the DHCP Server) for the Network Card with network address 0006298924F8. The following error occurred:
The semaphore timeout period has expired. . Your computer will continue to try and obtain an address on its own from the network address (DHCP) server.
Since I did not make any changes to my network configuration, I believe that the problem could be related to a reconfiguration of the Westell Router that was initiated by my provider. I could not find anything in the router's config pages that would let me change or view the settings for the DHCP service of a "Single Static IP" client, only for regular clients, where it is set to 5 days. Can someone confirm that a provider would actually go that far to stop customers from exposing a server?
Technically, I have no other explanation, but it still seems far-fetched to me.