Apple TV 3 drops ethernet connection on 2 seconds

The DHCP works fine for the airport.

If you use ethernet and a static IP address, then you'll have to choose an IP address outside of the DHCP lease range otherwise you can get IP address conflicts.

For example, if your DHCP range is set to 192.168.0.10 through 192.168.0.20 then you can use the IP address ranges 192.168.0.1 - 192.168.0.9 and 192.168.0.21 - 192.168.0.253 for statically assigned IP address.

Hope this helps

When your connections starts timing out, can you do arp -an in Terminal.app and see if you still have all MAC addresses in the ARP table? as in - your router's MAC address, or the host you're trying to ping?

If you do (and you have the time before it starts working again), can you flush the arp table (sudo arp -ad) and then see if your router's MAC address shows up in the ARP table again?

Also, try running a ping to your router's LAN IP address in one Terminal session, and maybe a ping to your router's WAN IP address in another while you're on Skype. See if all of them start timing out or just one of them. One more tool that I find useful is mtr - you may need to get the source and compile it yourself or use fink / macports or other package manager. When you get it, just run it to a destination somewhere on the Internet and it will show you which hop stops responding.

How to install software from sources (such as mtr) Requires Xcode to be installed:

• download the source archive (typically .tar.gz or .tar.bz2)
• uncompress the downloaded file (e.g. in Terminal.app run gzip -dc filename.tar.gz | tar -xvf -, which will typically create a new directory in the current directory, and put the content of the archive in there)
• navigate to the obtained folder in terminal
• run ./configure --prefix=/usr/local (please note, I like to install software from source into /usr/local to keep it away from binaries installed as part of the system; the --prefix=/usr/local option to configure will do just that)
• run make
• run sudo make install
• done!