Has nothing to do with your local systems or mobile devices nor router... They track IPs and associate IP's to accounts.
I also play this game and have 5 accounts.
I created a guild so that all accounts the main and 4 alias's can trade between guild members for free. Otherwise it costs you a forge point per trade outside of guild trade. I also left it open for any others who want to join to openly join up without worry of then getting kicked for not being active enough etc.
The maker of the game tracks internet connections and so only a single account can be active at a single time from a shared registered IP address that they keep track of. I was only able to run more than 1 account at a time if I was using my phone with 3G mobile internet and another account active on my home internet connection.
However once you log on to the mobile device with the other account they then know that two accounts are registered to IP addresses.
A friend of mine however was able to break out of this IP Address tracking by uninstalling the Forge of Empires AP from his mobile device including all cache data and disconnecting his mobile internet on his phone, and then reconnecting mobile internet and checking to see that the IP address was now different from mobile internet ISP's leased IP, then reinstall the game and be back to being able to run 2 accounts at the same time; BUT through 2 different internet connections a PC on broadband and a smart phone on 3G mobile network.
I only run one account at a time from my IP address these days and I created macros that perform unattended daily routines of gathering goods and gold from buildings that are on timers and so i logon to my main account and do what I need and then I set up my PC to run the macro which then performs the lengthy daily redundant stuff of tavern stuff and gathering gold and goods that were earned from the timed buildings.
It use to take me like 1.5 hours a day to manage 5 accounts, now its like 20 minutes on my main account and then walk away with the macro farming stuff for me on the 4 other accounts. But this macro is only allowed to logon to a single account at a time through my internet connection, so I can not have multiple systems online playing the same game at the same time. For one to be online the others have to be offline.
