Dlink DI-614+ router huge latency when connected to modem

[UncleWai]

When I connect the DI-614+ router to my cable modem, I would get a huge latency of 600+ms. The connection works perfectly fine when I hook the network card directly to the cable modem.
What will cause this problem?

 

[JackMDS]

I am Not familiar with this specific Router.

However, it might be an MTU problem, make sure that the MTU in the Router is set correctly and optimize the computers TCP/IP Stack.

Optimizing & Measuring the "Speed" of Internet Connection.

:sun:

 

[nweaver]

also could be cable related, a bad cable can cause huge latency. Swap cables around, and see if you can duplicate the problem going direct to modem.