Mikrotik L2TP with IPsec for mobile clients

I got some questions about how to configure Mikrotik to act as L2TP Server with IPsec encryption for mobile clients. I know this is not exactly in the line of this blog oriented on enterprise networks, but it’s network technology in the end so I’ll try to cover it here.

Before we start, please make sure that your Mikrotik build-in firewall is configured in such way that it can accept packets on the WAN interface. You can check my article on IPsec VPN Mikrotik to Cisco for firewall configuration.

Another important part is that I’m using RouterOS v6.24 in the below scenario. In earlier versions some configurations are a bit different, but you’ll figure it out as I will explain where is really important.

1. Add a new IP Pool

It’s not mandatory if you already have a IP Pool, but I assume you don’t and we need to add one.

GUI

IP > Pool

Add a new pool

CLI

L2TP Configuration

1. Configure L2TP Profile

Before adding a new L2TP Server, we need to add a new L2TP Profile. We can use also the default one, but I don’t like to mix things.

GUI

PPP > Profiles

The rest of values can be left on default value.

CLI

2. Add a L2TP-Server

GUI

PPP > Interface > L2TP Server

CLI

3. Add PPP Secrets

GUI

PPP > Secrets

Let the rest as default.

CLI

IPsec Configuration

On IPsec configuration, you can use the default configuration (like Proposals) but I would suggest to let those as default and add your new ones. In case that you already have some IPsec configuration which is already working and using the default configuration we don’t want to mess with that.

1. IPsec Proposals

GUI

IPsec > Proposals

CLI

Something to mention here. In version previous than 6.xx, you can pick only one encryption algorithm, if I remember correctly. You cannot add multiple algorithms (like 3des and aes-256 above). If this is the case, be sure to stay with 3des. I know it offer less security, but for some reason I could not force Microsoft Windows to work on L2TP via aes-256.

2. IPsec Peers

GUI

IPsec > Peers

CLI

IMPORTANT

The value of the Secret field above, MUST be the same as in L2TP Configuration, Step 2.
Also, if your RouterOS support only one encryption algorithm, then pick 3des.

3. IPsec Policies

GUI

CLI

Below, I’ll add two examples how to configure the iPhone and Microsoft Windows to work with the above configuration.

iPhone

Go to Settings, VPN section and Add VPN Configuration…

It will look like this:

iPhone L2TP Configuration

The Server is the public IP address or FQDN of your Mikrotik. Account and Password are the one defined in L2TP Configuration Step 3. (MYUSER and MYPASSWORD in the example above). Secret , is the IPsec Secret Key defined in L2TP Configuration Step 2. and IPsec Configuration Step 2. (MYKEY in the example).

PC with Microsoft Windows

1. Add a new VPN connection

Add New VPN Connection

2. Pick the option Use my Internet connection

Chose VPN type

3. Add Mikrotik L2TP Server details

Add L2TP Mikrotik details

4. Add the user and password

Add L2TP user

Add this point Windows 7 force me to hit Connect. I will not work yet. Please follow the next steps.

You need to reach the Properties of your new VPN connection.

5. Configure the VPN Security settings.

Be sure to have the settings like in image below, to force encryption and use mschap2 protocol.

L2TP VPN Security

6. Set the IPsec Secret key

Hit the Advanced button and set the IPsec key

L2TP IPsec Key

Hit Connect and it will work. If you have questions please be sure to add them to Comments.