I am having an issue with routers obtaining IP addresses from my fairly old motorola surfboard modem. An engenious ESR 9850 wireless N gigabyte router and my current airport extreme router both have the same issue. When the router is connected to the modem the router IP address is 184.108.40.206 and there are two DNS server addresses. When disconnected the router IP address is 192.168.100.1 which I believe is the surfboard address. and there are no DNS servers. Power cycling just the modem and not even power cycling the router will resolve the issue. I have to power cycle the modem and/or router every 2-3 days.When connected everything works fine including wireless, It seems to me that the modem may be the issue given that a new router is having the same issue as the old router. There are no trouble lights on the modem at any time. Shaw never finds a problem with the modem when I call. I would appreciate any insight into the issue.