Make sure your wireless is turned off, I have had (in testing at home) my wireless interfere with the ethernet and RB thinks you are using wireless now and not the ether port.
look whats in your network window, system prefs/network, make sure you only have normal connections in there like wifi, thernet, firewire and bluetooth, sometimes a location will be added like a PPPoE for stuff like cell phone tethering and this will 100% interfere will RB, again, this is from experience of what I have went through when RB first released the LINK feature. the network window should look like the pic I have attached, but like I said, you can have a couple of more maybe like bluetooth and/or firewire. Maybe it will help too in that same area to hit the settings gear at the bottom next to the + and - and "set service order" so ethernet is at the top of the list for priority when in use
check all cables, wiggle them back and forth, in and out and make sure they hold the connection to the switch, Some cables do not sit in right on the back of the 2000's so with some wiggling, they disconnect even though they still looked plugged in
- plug in 1 cdj directly into the ethernet port of the laptop and test, if it stays connected for a long period of time then it may be the switch causing the issue or the wire ran from the laptop to the switch during the gig. if that works, try the same with the other cdj, if that also works then swap the ethernet cables to see if you can narrow it down to a bad cable.
Most likely, I thing its with the network settings or config on the Macbook
I also, to speed up connections, have set a static IP in the ethernet connections for the decks to see quicker instead of waiting for DHCP to give an address to the laptop, Being that i only use the ethernet port for RB, I don't care that a static is set, keep in mind though that if you go to use the ethernet port later to get online, you have to set the port back to DHCP, you can do this by:
1 connect everything up, go to network setting and click on ethernet, you will see a DHCP address of something like 169.254.90.102
highlight and copy that address, or write it down
click on the configure IP drop down and choose manually boards the bottom
paste or type that address in and make sure the subnet still reads the 255 address, hit apply and you are all set
Now if you pull the ethernet from the laptop and plug it back in, the RB LINK icon will appear 10x faster because the mac is addressed, you don't have to wait for one to be given