/etc/ppp/ip-up logging script for https://superuser.com/questions/4904/how-to-selectively-route-network-traffic-through-vpn-on-mac-os-x-leopard

0-ReadMe.md

Attempt to manage vpn routing table with /etc/ppp/ip-up

Related Stackoverflow Question:
https://superuser.com/a/206826/55267

Related answer:
https://superuser.com/a/206826/55267

# setup
sudo touch /etc/ppp/ip-up
sudo vim /etc/ppp/ip-up # fill the script
sudo chmod +x /etc/ppp/ip-up
# tail the logs
sudo tail -f /var/log/ip-up.log

Tested on MacOS 10.13 and didn't work for me. Script doesn't get called.
This works, shebang was wrong. Thanks to athairus and Mark Gaensicke in the comments. 🙌

References

• route(8) [osx man page]
• Shebang (Unix) on Wikipedia

Edits

• 2022-11-02: I've updated the script to reflect suggested changes in comments and I've added logging of the command

ip-up.sh

#!/bin/sh
now=`date +%Y-%m-%d_%Hh%Mm%Ss`
logfile=/var/log/ip-up.log

echo "$0 called at $now with following params:" >> $logfile
echo "The VPN interface (e.g. ppp0): $1" >> $logfile
echo "Unknown, was 0, in my case: $2" >> $logfile
echo "IP of the VPN server: $3" >> $logfile
echo "VPN gateway address: $4" >> $logfile
echo "Regular (non-vpn) gateway for your lan connections: $5" >> $logfile

# Add 192.168.0.0 to 192.168.0.255 range to routing table on VPN interface
/sbin/route add -net 192.168.0.0/16 -interface $1 >> $logfile 2>&1

@GabLeRoux It's much easier nowadays.
As user run networksetup -listnetworkserviceorder to find out the name of the Network.

Run this to permanently add 172.20.20.0/24 with gateway 172.20.19.1
It's save to leave out the gateway :)

networksetup -setadditionalroutes "network name" 172.20.20.0 255.255.255.0 172.17.19.1

No need to rerun it :)