Falls off the network after few hours

[chirag]

Hi, my raspberry is connected to a display and it is directly connected to a router , both the raspberry and router configured with a static IP address. But initially i could ssh but after few hours when i ping i get the reply saying that "destination host unreachabe" il have to reboot the pi if to get the network back. But i want the network to be up all the time ? can i know how can i do this ?
is there any timeout like after few hours it will go off the network ?

[RaTTuS]

power ?
what does dmesg say when it drops off the network

[redhawk]

Are you using Wifi?? (If yes then you may need to disable power management).

Richard S.

[chirag]

Dmesg looks fine no errors

[chirag]

it is connected to a router directly ......im not using any USB Wi-Fi.