Shell scripts for bypassing PPTP VPN with intranet IP addresses (Mac OS X).

pptp-intranet-route.md

Add shell scripts

Add the following scripts under /etc/ppp/ (requires root privilege):

common

#!/bin/sh

# add/delete route only if device is in a specific intranet IP address block,
# change this value to YOUR network.
INTRANET_BLOCK='10.230'

# Element order in array determines interface priority
# you can add more interfaces to this list to meet your needs
NETWORK_INTERFACES=(
    'bridge0'   # Thunderbolt bridge
    'en0'       # WiFi
)

function is_intranet()
{
    local interface=$1
    local inet=$(/sbin/ifconfig "$interface" inet | /usr/bin/grep "inet $INTRANET_BLOCK")
    if [ -n "$inet" ]; then
        return 0
    else
        return 1
    fi
}

function add_route()
{
    local interface=$1
    local default_gateway=$(/usr/sbin/netstat -rn | /usr/bin/grep default | /usr/bin/grep "$interface" | /usr/bin/awk '{print $2}')
    /sbin/route -n add -net "$INTRANET_BLOCK" "$default_gateway"
}

function delete_route()
{
    /sbin/route delete -net "$INTRANET_BLOCK"
}

ip-up

#!/bin/sh

source /etc/ppp/common

for i in "${NETWORK_INTERFACES[@]}"
do
    if is_intranet $i; then
        add_route $i
        exit 0
    fi
done

ip-down

#!/bin/sh

source /etc/ppp/common

for i in "${NETWORK_INTERFACES[@]}"
do
    if is_intranet $i; then
        delete_route $i
        exit 0
    fi
done

Change file permissions

sudo chmod 755 [script]

Verify it works

netstat -nr