This might come in handy whenever you need to add one or more hosts to a running VPN connection (on Mac OS).

vpnhost.sh

#!/bin/sh
#
# vpnhost.sh - Add hosts/IP addresses to route through your VPN.
#
#   - Routed hosts are not persisted between restarts of your VPN software.
#   - The VPN's gateway route is hardcoded to be on the tun0 interface.
#   - Use of sudo is hard-coded too.
#   - Only works on OSX

VPN_IFACE=tun0

# Get a list of IP addresses from a hostname.  IP addresses pass through
# untouched.
get_ip_addresses () {
	# Cheap detection of an IP address...
	if [ `echo "$1" | grep -nc -E '^(\d+.?){4}$'` -eq "1" ] ; then
		echo "$1"
	else
		host "$1" | grep 'has address' | cut -d ' ' -f4
	fi
}

# Add an IP address to the routing table through $vpn_iface
add_ip_to_vpn () {
	echo "Adding VPN route for IP address $1... "
	sudo route add -host $1 -interface $VPN_IFACE
}

if [ $# -lt 1 ] ; then
	echo "Usage: $0 <IP Address|Hostname ...>"
	exit 1
fi

for arg in $@; do
	for ip_address in `get_ip_addresses "$arg"`; do
		add_ip_to_vpn "$ip_address"
	done
done