sudo touch /etc/network/if-up.d/ifupvpn
sudo vi /etc/network/if-up.d/ifupvpn
#!/bin/sh
if [ "$IFACE" = "ppp0" ]; then
ip route del 80.80.33.101 dev ppp0 proto kernel scope link src 10.100.20.1
fi
:wq
sudo chmod +x /etc/network/if-up.d/ifupvpn