Configuring site to site VPN using two m0n0wall boxes is a snap.

There are a couple of things you will want to know ahead of time.

  • The IP address or FQDN of both firewalls WAN interface.
  • Internal subnet of both networks.
  • The shared key (password).

Log into your firewall and head to the VPN/IPSec section. Click the + sign to get started. Assuming you are connecting two boxes across the internet, set the Interface to “WAN”. The Local subnet should be set to “LAN subnet” As the name implies, set the Remote subnet to the remote subnet in the form of “” (verify the subnet in the Interfaces: LAN page of the remote firewall). Set the Remote gateway to either the public IP or FQDN of the remote box.


Important: Using the settings Local & Remote subnet settings above both ends will have complete access to each others LAN. Modify these settings and/or your firewall rules accordingly.

Negotiation mode = aggressive For My identifier choose the appropriate item from the drop down list. I am using “Domain name” in the example image. The identified should be the domain name of your local firewall.

  • Encryption algorithm = Blowfish
  • Hash algorithm = SHA1
  • DH key group = 2
  • Lifetime default 28800
  • Authentication method = Pre-shared key
  • Pre-Shared Key = A password you will be using on both ends.


  • Protocol = ESP
  • Encryption algorithms check Blowfish
  • Hash algorithms check SHA1
  • PFS key group = 2
  • Lifetime default 86400


Once completed you will need to apply the same settings to the other m0n0wall system. Remote subnet, Remote gateway and My Identifier will need to be reversed.