Mirroring issues without Internet

I have a kit for keynote presentations containing an Apple TV and a wireless router so that I have a network independent of any outside networks.

The trouble is when using mirroring the appletv resets about every 10-15 min probably due to no Internet connection and it is also trying to set the date and time. Although while I'm writing this I'm wondering if it just shuts off due to inactivity like going to sleep. Ill have to check on that.

Can anyone confirm if what I'm trying to do is possible without Internet connection but still be stable for an hour of mirroring Time.

Specs wifi: linksys 750 with an Ethernet to Apple TV

Ipad 2 on 5ghz mirroring

Keynote file is usually about 250mb in size but is used over an hour timespan.