How do I get my LAN computers to reach the Internet?

I am having a problem with my wireless network. Computers on my LAN work just fine, and I can connect to and change settings on my wireless router. But ever since my ISP updated its DNS servers, my LAN computers just cannot reach the Internet.

It sounds like the DNS update only made it as far as your router, not your LAN. To check the DNS settings on a Windows PC, open a command prompt window, type "ipconfig /all" and look for the DNS Server(s) listed under the wireless adapter. You should either see the IP address of your wireless router or the IP address(es) of your ISP's current DNS Server(s).

If you see the IP address of your wireless router, the router's built-in DNS Server may need to be updated to forward unresolved requests to your ISP's DNS Servers. Correcting this depends on your wireless router, but search your router's configuration pages for DNS Server settings. If you cannot find anything to change or refresh, consider resetting your wireless router to factory default and starting from scratch. (It is always a good idea to review and save your existing configuration first!)

If you see the IP address(es) of your ISP's old DNS Server(s), the problem may lie with the router's DHCP Server or the PC's connection settings. Open the wireless connection's Properties Panel, highlight "Internet Protocol" and click on Properties. If "Use the following DNS servers addresses" is checked, update the IP address listed under that section. Otherwise ("Obtain

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DNS server addresses automatically"), the router's DHCP Server may need to be reconfigured to supply new DNS Server addresses. Search your router's configuration pages for DHCP Server settings. After making this change to your router, use a command prompt window on the PC to type "ipconfig /renew" and then check those addresses again to verify they now match your ISP's current DNS Servers.

By the way, to test how hostnames are resolved on a Windows PC, open a command prompt window and type "nslookup." At the ">" prompt, type any hostname that you want to resolve. You can temporarily change the DNS Server by typing "server IPaddress" where IPaddress is the DNS Server you want to consult. To leave nslookup, type "exit."

This was first published in March 2007

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