This page discusses the concepts of addressing in OpenVPN.

Addressing in OpenVPN depends on the [in use. The 3 types of possible server/client addressing styles are explained in the Topology page and are:

subnet:: The preferred topology for server/client steups

net30:: The deprecated /30 subnet allocation (best to avoid this)

p2p:: peer-to-peer addressed setups (non-Windows only; uses Point-To-Point, or PtP networking)

Note that with net30, non-Windows clients will configure addressing as PtP anyway; Windows uses the /30 as a virtual "network."

Another operating mode is when you don't run either side as a server, which is when both are using `--mode p2p --topology p2p`. In this case, each end sets its own addressing. The addresses chosen here are completely arbitrary and only define the local verses remote sides. Addressing doesn't even need to be adjacent and "any" 2 addresses can be used.

If you intend to create a server that multiple clients connect to, you cannot use this mode. Also note that Windows clients do not support this.

In server mode, an addressing pool is commonly used; when used, clients that do not have server-side static addressing configured will be allocated an IP dynamically from this pool.

It is possible to have the server allocate a static IP to a client based on its commonName. This is done by way of an `--ifconfig-push` command in either a ccd file or (as an advanced alternative) by `--client-connect` script.

It is important to note that defining static addressing with an address that is also in the pool will result in problematic behavior if that IP was already allocated to another client. For this reason it is critical to reduce your pool range and assign static addresses that are outside the defined pool.

This means you cannot use the `--server` directive with static addressing as it consumes the entire network for the pool; instead, expand the directive and reduce the pool range to avoid problems.

The examples below use 10.8.0.0/24 as the VPN network and include samples for both full-pool allocation, and a reduced allocation with static addressing for 2 clients called 'client1' and 'client2'.

Since the TLS setup is not the focus here, the `--pkcs12` is used here; your setup will likely be different. Addressing is the important part of these examples. Also note that the `--topology` directive is often pushed, and is in these examples.

* server config:

* client config:

* server config:

* server's `/vpn/ccd-dir/client1` file:

* server's `/vpn/ccd-dir/client2` file:

* client config:

Note that net30 is the default topology (as of OpenVPN 2.3) and need not be declared explicitly with `--topology`.

* server config:

* client config:

* server config:

* server's `/vpn/ccd-dir/client1` file:

* server's `/vpn/ccd-dir/client2` file:

* client config:

This topology is only valid when none of your clients are Windows. The benefit is that you can use the entire network range. This can be beneficial when using smaller networks, such as a /29, /30, or even a /31 (normally unusable on "traditional" Ethernet-style networks.)

An advanced example is also shown at the end where you can use 100% of a given network for client IPs since PtP addressing does not have to be contiguous.

All these examples push the assigned IPs from the server, so they use a **single** client config common to all examples:

* client config:

In this example, we assign the following addressing:

* VPN server: 10.8.0.0

* client1: 10.8.0.1

* client2: 10.8.0.2

* dynamic IPs assigned to other clients: 10.8.0.100 - 10.8.0.199

* (The IP 10.8.0.255 is used as a common peering IP and not routable)

* server config:

* server's `/vpn/ccd-dir/client1` file:

* server's `/vpn/ccd-dir/client2` file:

In this example, we assign the following addressing, assigning 4 clients out of the network 203.0.113.252/30. The VPN server uses RFC1918 locally, and a matching RFC1918 is used by clients as the peering address.

* VPN server: 192.168.222.0 (peering with 192.168.222.1)

* client1: 203.0.113.252

* client2: 203.0.113.253

* client3: 203.0.113.254

* client4: 203.0.113.255

* server config:

* server's `/vpn/ccd-dir/client1` file:

* server's `/vpn/ccd-dir/client2` file:

* server's `/vpn/ccd-dir/client3` file:

* server's `/vpn/ccd-dir/client4` file: