VPN

A VPN (Virtual Private Network) allows you to establish a secure and encrypted connection between two or more systems using a public network, like the Internet.

The system supports two types of VPNs:

  1. roadwarrior: connect a remote client to the internal network
  2. net2net or tunnel: connect two remote networks

OpenVPN

OpenVPN lets you easily create VPN connections, It brings with numerous advantages including:

  • Availability of clients for various operating systems: Windows, Linux, Apple, Android, iOS
  • Multiple NAT traversal, you do not need a dedicated static IP on the firewall
  • High stability
  • Simple configuration

Roadwarrior

The OpenVPN server in roadwarrior mode allows connection of multiple clients.

Supported authentication methods are:

  • System user and password
  • Certificate
  • System user, password and certificate

The server can operate in two modes: routed or bridged. You should choose bridged mode only if the tunnel must carry non-IP traffic.

To allow a client to establish a VPN:

  1. Create a new account: it is recommended to use a dedicated VPN account with certificate, avoiding the need to create a system user.

    On the other hand, it’s mandatory to choose a system account if you want to use authentication with user name and password.

  2. Download the file containing the configuration and certificates.

  3. Import the file into the client and start the VPN.

Tunnel (net2net)

When creating an OpenVPN net2net connection, a server will have the master role. All other servers are considered as slaves (clients).

A client can be connected to another NethServer or any other firewall which uses OpenVPN.

All tunnels use OpenVPN routed mode, but there are two kind of topologies: subnet and p2p (Point to Point)

Topology: subnet

This is the recommended topology. In subnet topology, the server will accept connections and will act as DHCP server for every connected clients.

In this scenario

  • the server will authenticate clients using TLS certificates
  • the server can push local routes to remote clients
  • the client will be able to authenticate with TLS certificates or user name and password

Topology: P2P

In p2p topology, the administrator must configure one server for each client.

In this scenario:

  • the only supported authentication method is the PSK (Pre-Shared Key). Please make sure to exchange the PSK using a secure channel (like SSH or HTTPS)
  • the administrator must select an IP for both end points
  • routes to remote networks must be configured on each end point

To configure a tunnel, proceed as follow:

  1. Access the tunnel server and open the OpenVPN tunnels page, move to Tunnel servers tab and click on Create new button
  2. Insert all required fields, but please note:
    • Public IPs and/or public FQDN, it’s a list of public IP addresses or host names which will be used by clients to connect to the server over the public Internet
    • Local networks, it’s a list of local networks which will be accessible from the remote server. If topology is set to p2p, the same list will be reported inside the client Remote networks field
    • Remote networks, it’s a list of networks behind the remote server which will be accessible from hosts in the local network
  3. After the configuration is saved, click on the Download action and select Client configuration
  4. Access the tunnel client, open the OpenVPN tunnels page, move to Tunnel clients tab, click on Upload button

Advanced features

The web interface allows the configuration of advanced features like:

  • on the client, multiple addresses can be specified inside the Remote hosts field for redundancy; the OpenVPN client will try to connect to each host in the given order
  • WAN priority: if the client has multiple WAN (red interfaces), the option allows to select the order in which the WAN will be used to connect to the remote server
  • protocol: please bear in mind that OpenVPN is designed to operate optimally over UDP, but TCP capability is provided for situations where UDP cannot be used
  • cipher: the cryptographic algorithm used to encrypt all the traffic. If not explicitly selected, the server and client will try to negotiate the best cipher available on both sides
  • LZO compression: enabled by default, can be disabled when using legacy servers or clients
Legacy mode

Tunnels can still be created also using Roadwarriors accounts.

Steps to be performed on the master server:

  • Enable roadwarrior server
  • Create a VPN-only account for each slave
  • During the account creation remember to specify the remote network configured behind the slave

Steps to be performed on the slave:

  • Create a client from the Client page, specifying the connection data to the master server.
  • Copy and paste the content of downloaded certificates from the master configuration page.

IPsec

IPsec (IP Security) protocol is the ‘de facto’ standard in VPN tunnels, it’s tipically used to create net to net tunnels and it’s supported from all manufacturers. You can use this protocol to create VPN tunnels between a NethServer and a device from another manufacturer as well as VPN tunnels between 2 NethServer.

Tunnel (net2net)

IPsec is extremely reliable and compatible with many devices. In fact, it is an obvious choice when you need to create net2net connections between firewalls of different manufacturers.

Unlike OpenVPN configuration, in an IPsec tunnel, firewalls are considered peers.

If you are creating a tunnel between two NethServer, given the firewalls A and B:

  1. Configure the server A and specify the remote address and LAN of server B. If the Remote IP field is set to the special value %any, the server waits for connections from the other endpoint.
  2. Configure the second firewall B by mirroring the configuration from A inside the remote section. The special value %any is allowed in one side only!

If an endpoint is behind a NAT, the values for Local identifier and Remote identifier fields must be set to custom unique names prepended with @. Common names are the geographic locations of the servers, such as the state or city name.