Computer Help and Support

Your router talks to your DSL modem and in the periodic handshaking is given the IP address of AT&T's DNS server. A DNS server translates www.democraticunderground.com into 35.175.60.16. The IP address is like a street address and zip code for the internet. DNS server addresses are changed now and then for service or maintenance. When your router powers up, part of the initialization is getting the DNS server address from your modem.

There are options here. You can manually configure your router to use a specific DNS server. You can also set a specific DNS server for you PC's network connection.

All that is not so interesting but the best advice is to get a new router. Your existing router is either losing the DNS server's address in its memory or messages are dropping when the address is updated.

Edit to add: If your DSL modem is also 9 years old it may be developing defects. It may be time to replace the modem as well. The recommendation to switch to cable or fiber is a quite sound.

Routers: Your router likely has a WAN port to connect to the DSL modem and 4 LAN ports for Ethernet devices (PCs, printers...). It probably also has WiFi 802.11n which is no longer the fastest option but if you don't really use WiFi, not a big deal. Perfectly good routers with newer faster WiFi are available on Amazon and Newegg for ~ $60 - 100.