Mobile devices can switch between Wi-Fi and mobile network seamlessly
without dropping any connectivity.
Supercedes OpenVPN and IPSec, which are obsolete and insecure.
# Requirements
I assume you have a host in the cloud, with world accessible network address and ports, that can access blocked websites freely outside of your country or Internet filtering system.
We are going to enable ip4 and ipv6 on our vpn. The tutorial assumes ipv6 is working. Check that it *is* working by pinging your server `ping -6 «server»`, then ssh in to your server and attempt to `ping -6 «something»`
It may well happen that your server is supposed to have an ipv6 address and /64 ipv6 subnet, but something is broken.
This configuration file is for two clients, one of which is a bitcoin peer for which port forwarding is provided, and to provide them a nat translated IPv4 address, and an IPv6 address on a random /112 subnet of the vpn servers /64 subnet. Adjust to taste. IPv6 is tricky.
Use a command-line text editor like Nano to create a WireGuard configuration file on the Debian server. `wg0` will be the network interface name.
```bash
sudo nano /etc/wireguard/wg0.conf
```
Copy the following text and paste it to your configuration file. You need to use your own server private key and client public key.
The curly braces mean that you do not copy the text inside the curly braces, which is only there for example. You have to substitute your own private key (since everyone now knows this private key), and your own client public key., mutas mutandis.
- **Address**: Specify the private IP address of the VPN server. Here I’m using the 10.10.10.0/24 network range, so it won’t conflict with your home network range. (Most home routers use 192.168.0.0/24 or 192.168.1.0/24). 10.10.10.1 is the private IP address for the VPN server.
- **PrivateKey**: The private key of VPN server, which can be found in the `/etc/wireguard/server_private.key` file on the server.
- **ListenPort**: WireGuard VPN server will be listening on UDP port 51820, which is the default.
- **PublicKey**: The public key of VPN client, which can be found in the `/etc/wireguard/public.key` file on the client computer.
- **AllowedIPs**: IP addresses the VPN client is allowed to use. In this example, the client can only use the 10.10.10.2 IP address inside the VPN tunnel.
Change the file permission mode so that only root user can read the files. Private keys are supposed to be _private_,
We need to set up IP masquerading in the server firewall, so that the server becomes a virtual router for VPN clients. I will use UFW, which is a front end to the iptables firewall. Install UFW on Debian with:
``` bash
apt -qy install ufw
```
If ufw is already installed and running
``` bash
ufw disable
```
First, you need to allow SSH traffic.
```bash
ufw allow 22/tcp
```
Next, find the name of your server’s main network interface.
To configure IP masquerading, we have to add iptables command in a UFW configuration file.
```bash
nano /etc/ufw/before.rules
```
By default, there are some rules for the `filter` table. Add the following
lines at the end of these default rules. Replace `eth0` with your own
network interface name.
# NAT table rules
*nat
:POSTROUTING ACCEPT [0:0]
-F
-A POSTROUTING -o «eth0» -j MASQUERADE
# End each table with the 'COMMIT' line or these rules
# won't be processed
COMMIT
"MASQUERADE" is NAT packet translation. This puts your IP4
forwarded network addresses behind a NAT firewall, so that they appear
on the internet with network address of the server.
If you want to NAT translate your IPv6 addresses, will have to do
something similar in `/etc/ufw/before6.rules`. But you usually have lots
of IPv6 addresses, so you seldom want to nat translate IPv6
In Nano text editor, you can go to the end of the file by pressing `Ctrl+W`, then pressing `Ctrl+V`.
```terminal_image
-A ufw-before-input -p udp -d 239.255.255.250 --dport 1900 -j ACCEPT
# don't delete the 'COMMIT' line or these rules won't be processed
COMMIT
# NAT table rules
*nat
:POSTROUTING ACCEPT [0:0]
-F
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
```
The above lines will append `-A` a rule to the end of the`POSTROUTING` chain of the `nat` table. It will link your virtual private network with the Internet. And also hide your network from the outside world. So the Internet can only see your VPN server’s IP, but can’t see your VPN client’s IP, just like your home router hides your private home network.
Like your home router, it means your client system behind the nat has no open ports.
As always «...» means that this is an example value, and you need to substitute your actual value. "_Mutas mutandis_" means "changing that which should be changed", in other words, watch out for those «...» .
Note that the last line is intended to leave your clients naked on the IPv6
global internet with their own IPv6 addresses, as if they were in the cloud
Now if you list the rules in the POSTROUTING chain of the NAT table by using the following command:
```bash
iptables -t nat -L POSTROUTING
```
You can see the Masquerade rule.
```terminal_image
:~# iptables -t nat -L POSTROUTING
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
MASQUERADE all -- anywhere anywhere
```
## Install a DNS Resolver on the Server
Since we will specify the VPN server as the DNS server for client, we need to run a DNS resolver on the VPN server. We can install the bind9 DNS server.
```bash
apt install bind9
```
Once it’s installed, BIND will automatically start. You can check its status with:
-`Address`: Specify the private IP address of the VPN client.
-`DNS`: specify 10.10.10.1 (the VPN server) as the DNS server. It will be configured via the `resolvconf` command. You can also specify multiple DNS servers for redundancy like this: `DNS = 10.10.10.1 8.8.8.8`
-`PrivateKey`: The client’s private key, which can be found in the `/etc/wireguard/private.key` file on the client computer.
-`PublicKey`: The server’s public key, which can be found in the `/etc/wireguard/server_public.key` file on the server.
-`AllowedIPs`: 0.0.0.0/0 represents the whole IPv4 Internet, which means all IPv4 traffic to the Internet should be routed via the VPN. ::/0 represents the whole IPv6 Internet. If you specify one but not the other, and your client has both IPv4 and IPv6 capability, only half your traffic will go through the vpn. If your client has both capabilities, but your vpn does not, this is bad, but things still work.
-`Endpoint`: The public IP address and port number of VPN server. Replace 123.45.67.89 with your server’s real public IP address and the port number with your server’s real port number.
-`PersistentKeepalive`: Send an authenticated empty packet to the peer every 25 seconds to keep the connection alive. If PersistentKeepalive isn’t enabled, the VPN server might not be able to ping the VPN client.
Save and close the file.
Change the file mode so that only root user can read the files.
Now go to this website: `http://icanhazip.com/` to check your public IP address. If everything went well, it should display your VPN server’s public IP address instead of your client computer’s public IP address.
You can also run the following command to get the current public IP address.
Install the `tshark` network traffic analyzer on the server. Tshark is the command-line version of Wireshark.
```bash
apt install -qy tshark
adduser «your-username» wireshark
su -l «your-username»
tshark -i «eth0» "udp port «51820»"
```
If you are asked “_Should non-superusers be able to capture packets?_”,
answer _Yes_. Once it’s installed, run the following command to add your
user account to the `wireshark` group so that you can capture packets.
If the WireGuard client is able to connect to UDP port «51820» of the server, then you will see packets being captured by tshark like below. As you can see, the client started the handshake initiation, and the server sent back a handshake response. Once the connection is established, the client sends keepalive packets.
If the WireGuard client can not connect to UDP port 51820 of the server, then you will only see handshake initiation packets. There’s no handshake respsonse.
If your VPN still doesn’t work, try restarting the VPN server and client.
# Adding Additional VPN Clients
WireGuard is designed to associate one IP address with one VPN client. To add more VPN clients, you need to create a unique private/public key pair for each client, then add each VPN client’s public key in the server’s config file (`/etc/wireguard/wg0.conf`) like this:
Each VPN client will have a static private IP address (10.10.10.2,
10.10.10.3, 10.10.10.4, etc). Restart the WireGuard server for the changes
to take effect.
Then add WireGuard configuration on each VPN client as usual.
## Configure VPN Client on iOS/Andorid
Install the `WireGuard` app from the App store. Then open this app and click the `Add a tunnel` button.
You have 3 methods to create a new WireGuard tunnel.
- create from file or archive
- create from QR code
- Create from scratch
"Create from scratch" means that the Wireguard app gives you a private and public key pair, and an empty wg-client.conf file that you populate in
the wireguard app ui. This is likely to result in a lot of typing where you
are bound to do a typo, even though the correct and working information
is already on your debian server and client and you would like to just copy
and paste it.
Create from QR code means that you create `ios.conf` in your client, as before for debian, add the public key to your server `wg0.conf` as before for debian, restart the server as before, and then generate the QR code with
It’s not recommended to use _policy routing_, _split tunneling_, or _VPN kill switch_ in conjunction with each other. If you use policy routing, then you should not enable split tunneling or VPN kill switch, and vice versa.
## Policy Routing
By default, all traffic on the VPN client will be routed through the VPN
server. Sometimes you may want to route only a specific type of traffic,
based on the transport layer protocol and the destination port. This is
known as policy routing.
Policy routing is configured on the client computer, and we need to stop
the WireGuard client process and edit the client configuration file.
```bash
systemctl stop wg-quick@wg0.service
nano /etc/wireguard/wg-client0.conf
```
For example, if you add the following 3 lines in the `[interface]` section,
then WireGuard will create a routing table named “1234” and add the ip rule
into the routing table. In this example, traffic will be routed through VPN
server only when TCP is used as the transport layer protocol and the
destination port is 25, i.e, when the client computer sends emails.
```default
Table = 1234
PostUp = ip rule add ipproto tcp dport 25 table 1234
Save and close the file. Then start WireGuard client again.
## Split Tunneling
By default, all traffic on the VPN client will be routed through the VPN
server. Here’s how to enable split tunneling, so only traffic to the
`10.10.10.0/24` IP range will be tunneled through WireGuard VPN. This is useful when you want to build a private network for several cloud servers, because VPN clients will run on cloud servers and if you use a full VPN tunnel, then you will probably lose connection to the cloud servers.
Edit the client configuration file.
```default
nano /etc/wireguard/wg-client0.conf
```
Change
```default
AllowedIPs = 0.0.0.0/0
```
To
```default
AllowedIPs = 10.10.10.0/24
```
So traffic will be routed through VPN only when the destination address is
in the 10.10.10.0/24 IP range. Save and close the file. Then restart WireGuard client.
sudo systemctl restart wg-quick@wg0.service
## VPN Kill Switch
By default, your computer can access the Internet via the normal gateway
when the VPN connection is disrupted. You may want to enable the kill switch
feature, which prevents the flow of unencrypted packets through
non-WireGuard interfaces.
Stop the WireGuard client process and the client configuration file.
```default
systemctl stop wg-quick@wg0.service
nano /etc/wireguard/wg-client0.conf
````
Add the following two lines in the `[interface]` section.
```default
PostUp = iptables -I OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT
PreDown = iptables -D OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT
