On a Mac, set a route after connecting to a SoftEther VPN

setvpnroute.sh

#!/bin/bash
# Set up a route to the be used when logged into
# AWS SoftEther VPN
# VPN IP addresses should be in the 192.168.99 subnet after connection is made.
# The gateway for the route is usually set to the address received via DHCP.
# On Mac OSX the route sent by DHCP is ignored and must be set manually
echo "Setting up routing for AWS VPN interface....."
INTFC=$(/sbin/ifconfig | grep ppp | awk -F: '{print $1}')
if [ -z $INTFC ]; then
  echo "No ppp interface found. Check VPN connection"
  exit 1
else
  echo "VPN interface is $INTFC ....."
fi
GW=$(/sbin/ifconfig | grep 192.168.99 | awk '{print $2}')
if [ -z $GW ]; then
  echo "No IP address found for 192.168.99 network. Check VPN connection."
  exit 1
else
  echo "VPN IP address is $GW"
  /sbin/route -n add -net 172.31.0.0/16 $GW
fi
echo ""
if netstat -rn | grep 172.31; then
  echo "ROUTE ADDED for AWS network"
else
  echo "ERROR adding route for AWS. Consult system administrator."
fi