I have a dlinkwbr-2310 router.When my router and comtrend modem are connected directly,I no longer have internet access on my home computer.As soon as I unplug router from modem,it's back.dlink tech support couldn't help as well as my isp tech support.What do I do next?

What do I do next?

Post the current IP configuration settings for the modem, router, and computer when they are all connected. Alternatively, suggest you find someone local with networking knowledge who can troubleshoot onsite.

Possibly ppoe interference, wireless settings screwing up defaults in modem when router connected.

You'll probably end up having to reset both, then setting up your modem into bridge mode, disabling any wireless. After that you usually have to configure the router to Bridge with the modem via PPOE and have that control the settings. This is usually common with DSL, not so much with cable or fiber. If you do determine this needs to be done, have your ISP walk you through it, they know all the tricks and settings.