OpenVPN between Mikrotik and OpenWRT

This is a page full of details, for the intro and how to set up Windows and Linux clients, see OpenVPN.

I am writing this while testing with three virtual machines on a Mac. Once I have the steps down, I will be transferring everything over to a Buffalo WZR WiFi access point running OpenWRT 14.xx and a Mikrotik RB750 running RouterOS 5.27.

I am running my virtual machines on VirtualBox. I use images downloaded from OpenWRT and Mikrotik and install them into very minimal setups. This is handy, they boot FAST and I don't risk cutting myself off from the remote end as I do tests and experiment.

The main reasons I chose to use OpenVPN over other options (today) are:

1. I can directly route packets so I don't need to mess with NAT at one end as with PPTP
2. My endpoint is hiding behind several layers of access points and routers that I don't control. OpenVPN works fine in this case.

The virtual network

Plover (Macintosh)
   192.168.56.1

    LAN (This will be the LAN in my house)

   192.168.56.101
VM1 = Router #1, OpenWRT Barrier Breaker
     76.0.0.1

     Internet

     76.0.0.2
VM2 = Router #2, Mikrotik RouterOS 6.23
    192.168.2.1

    REMOTE LAN (this will be the CDS OFFICE LAN)

   192.168.2.2
VM3 = Remote Debian server

Creating the certificate and key files

I do this on a Ubuntu Linux box, it's the easiest way. It is also possible to install easy-rsa on the OpenWRT device and create the files there.

This Certificates with Easy-RSA Mikrotik page has instructions on how to create the keys. Here is an abridged version.

sudo -i
apt-get install openvpn easy-rsa
cd /usr/share 
cp -r easy-rsa /etc/openvpn
cd /etc/openvpn/easy-rsa
emacs vars
source vars
# This creates the ca.crt file in keys/
./pkitool --initca

Create the files for the Mikrotik RB750 "server"; remember your password!

./pkitool --pass --server rb750
# Convert key file to pem file format
openssl rsa -in keys/rb750.key -out keys/rb750.pem

# Create files for the OpenWRT "client"
./pkitool openwrt
openssl rsa -in keys/openwrt.key -out keys/openwrt.pem
./build-dh

# Copy the server files to the rb750
cd keys
ftp 76.0.0.2
bin
put rb750.crt
put rb750.pem
put ca.crt
cd ..

# Copy the client files to the router
cd keys
scp openwrt.crt openwrt.pem ca.crt 192.168.56.101:/tmp

The OpenWRT router

Refer to http://wiki.openwrt.org/doc/howto/vpn.openvpn I am not going to copy all the instructions here, just go look at that page now.

ssh [email protected]
opkg update
opkg install openvpn-openssl
mkdir /etc/openvpn
mv /tmp/openwrt.* /tmp/ca.crt /etc/openvpn

The Mikrotik router

Refer to same Mikrotik page as mentioned above, http://wiki.mikrotik.com/wiki/OpenVPN

Import the three files transferred in the "create" section above.

/certificate
import file=rb750.crt
import file=rb750.pem
import file=ca.crt

# This will let you have many OpenVPN clients
/ip pool add name=ovpn-pool ranges=10.10.10.2-10.10.10.50

/ppp profile 
add change-tcp-mss=default comment="" local-address=192.168 \
name="ovpn_profile" only-one=default remote-address=ovpn-pool \
use-compression=default use-encryption=required use-vj-compression=default
/ppp secret 
add caller-id="" comment="" disabled=no limit-bytes-in=0 \
limit-bytes-out=0 name="ovpn" password="password" routes="" service=any

# If you don't already have these defined, 
/ip address
add address=10.8.0.1/24 interface=ether1 comment="Tunnel" 
add address=192.168.2.1/24 interface=ether1 comment="LAN" 
add address=76.0.0.2/24 interface=ether2 comment="Internet" 

/ip route
add dst-address=10.8.0.0/24 gateway=10.8.0.1 comment="OVPN"
add dst-address=192.168.4.0/24 gateway=10.8.0.1 comment="OVPN"
add gateway=76.0.0.2 comment="Internet"

/interface ovpn-server server 
set auth=sha1,md5 certificate=router_cert \
cipher=blowfish128,aes128,aes192,aes256 default-profile=ovpn_profile \
enabled=yes keepalive-timeout=disabled max-mtu=1500 mode=ip netmask=29 \
port=1194 require-client-certificate=no

/ip firewall filter 
add action=accept chain=input comment="OpenVPN" disabled=no dst-port=1194 protocol=udp

The "remote" server

I have a generic Debian server installed already in a VirtualBox machine, so I used it as the far end of my network to allow me to test connectivity through the two routers.

Tests

Start the client

/etc/init.d/openvpn start
cat /tmp/openvpn.log
ifconfig tun0

Make sure you can reach each of the routers and the Debian server from the Mac, and that you can reach each of the routers and the Mac from the Debian server.