So this is on my friends network, recently he got a VPN after he complained about youtube stuttering and I suggested he try a VPN.
So he did and it worked great, but he mentioned that if he leaves the VPN on for a long enough period his router/modem will start to constantly reboot itself until he disables the VPN.
There are only 2 internet providers where we live, Time Warner, and AT&T, and with his current situation he can only get service from AT&T.
He doesnt want to contact their customer support because as he says they are the worst ever at their job.
Anyone know why his router/modem is constantly rebooting itself?
I'm having a hard time coming up with an explanation that isn't a conspiracy of the ISP trying to discourage the use of a vpn. They probably don't like not being able to use caching servers to reduce actual internet traffic. Or they could be rebooting to disrupt torrenting.
I would pester the customer support of the ISP & of the VPN provider, and if it can't be resolved i would contact the legal department of the VPN provider:
Because if the isp is actively hindering the vpn provider's ability to do business, the vpn provider can absolutely crush the ISP on the legal path. Which means that the isp is probably going to give in, and stop it.
In the meantime try to find out exactly how long it takes until the router goes bonkers, & whether the amount of traffic that is being transfered over the vpn is affecting that time:
compare the time of uninterrupted vpn connection with & without traffic.
It always helps when you have measurements to back up your argument.
I'd also try and get CPU usage and log records out of the device; it's sounds more likely the router/modem is having a hard time dealing with packet encapsulation. You could also perform a packet capture on the client side to check for keepalives or heartbeats; the University I'm studying at provides VPN using PPTP which, when connected, uses PPP echo requests to keep the connection open.
This smells like AT&T being evil. I agree with Fluffymace. Log what is happening up until when the modem starts having problems, and do this over a period of time, (about a week) so you have solid evidence of the activity. Then harass AT&T, and if they blow you off, contact the VPN provider and let them know what is happening, and share the data you have logged. If you aren't willing to put the work in, the big ISPs will just ignore you and continue their tomfoolery.