VPN Client and IP tables

I have a Debian 8.7 IoT Version on a Beaglebone Black device which is connected to the Internet using a GSM Modem. I installed a VPN client (zerotier ) which joins a virtual network. Something changes the default route and my Internet is no longer working. netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 zt0 0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 ppp0 10.64.64.64 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 10.241.0.0 0.0.0.0 255.255.0.0 U 0 0 0 zt0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 zt0 192.168.6.0 0.0.0.0 255.255.255.252 U 0 0 0 usb1 192.168.7.0 0.0.0.0 255.255.255.252 U 0 0 0 usb0 How can I ensure the default communication is routed over ppp0 and only 10.241.0.0/16 over zt0. After adding the default GW, I get the following Table: Destination Gateway Genmask Flags MSS Window irtt Iface 0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 zt0 0.0.0.0 100.97.168.1 0.0.0.0 UG 0 0 0 ppp0 0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 ppp0 I found out what adds the entry: Oct 02 12:55:48 PTMH7 connmand: zt0 {add} route 0.0.0.0 gw 0.0.0.0 scope 253 How can I prevent ConnMan from doing so?