When connecting to my own VPN server on a specific network, called public-network, my Mac disconnects the VPN connection after 2 minutes and 30 seconds.

I have performed several tests and this is the result:

• It works fine until the 2:30 mark
• It doesn't matter which Mac I use, it still disconnects
• It doesn't matter which client I use, all of the following does the same: OSX system client, HMA! Pro VPN and Shimo
• It doesn't matter which protocol I use, at least all of these protocols does the same: PPTP, OpenVPN and L2TP over IPSec
• The same thing happens using my own VPN server and HMA!'s VPN server.
• All other clients (Windows/iPhone) can use any of these VPN servers and protocols without problem on public-network
• On OSX, all the protocols, clients and servers works fine on any other network

So it seems that it is the combination of OSX, VPN & public-network that causes this.

This is the syslog from my VPN server, when the disconnection happens:

Feb  2 12:04:32 raspberrypi pptpd[31400]: CTRL: EOF or bad error reading ctrl packet length.
Feb  2 12:04:32 raspberrypi pptpd[31400]: CTRL: couldn't read packet header (exit)
Feb  2 12:04:32 raspberrypi pptpd[31400]: CTRL: CTRL read failed
Feb  2 12:04:32 raspberrypi pptpd[31400]: CTRL: Reaping child PPP[31401]
Feb  2 12:04:32 raspberrypi pppd[31401]: Hangup (SIGHUP)
Feb  2 12:04:32 raspberrypi pppd[31401]: Modem hangup
Feb  2 12:04:32 raspberrypi pppd[31401]: Connect time 2.5 minutes.
Feb  2 12:04:32 raspberrypi pppd[31401]: Sent 3963649 bytes, received 362775 bytes.
Feb  2 12:04:32 raspberrypi pppd[31401]: MPPE disabled
Feb  2 12:04:32 raspberrypi pppd[31401]: Connection terminated.
Feb  2 12:04:32 raspberrypi pppd[31401]: Exit.
Feb  2 12:04:32 raspberrypi pptpd[31400]: CTRL: Client <ip-adress> control connection finished