Openvpn safe kill switch / isolate vpn connection using linux routing table (no iptables needed)

vpn_intrd.sh

#!/bin/bash

## Openvpn safe kill switch / isolate vpn connection using linux routing table (no iptables needed)
# Author: intrd@dann.com.br

# flush the entire routing table (incl cache)
sudo ip route flush table main
sudo ip route flush cache

# route the wan network but not a gateway
sudo route add -net 10.100.55.0 netmask 255.255.255.0 dev eth0

# shuffle and choose a rand ovpn file
VPNFILE=$(find /vpn/ -name *.ovpn|shuf|head -n1)

# add a route for all remote ips found in ovpn files pointing to wan gateway
cat $VPNFILE | grep -P "remote \d"|cut -d" " -f2|sort -u | while read ip; do sudo route add $ip gw 10.100.55.1 eth0; done

# run ovpn w/ provided creds
sudo openvpn --config $VPNFILE --auth-user-pass /vpn/cred.txt

## vpn_restore.sh - to restore (if needed)

# sudo route add -net 10.100.55.0 netmask 255.255.255.0 dev eth0
# sudo route add default gw <YOURLOCALGW> eth0