Set Up OpenConnect VPN Server (ocserv) on Debian 10 Buster with Let’s Encrypt

This tutorial is going to show you how to run your own VPN server by installing OpenConnect VPN server on Debian 10 Buster. OpenConnect VPN server, aka ocserv, is an open-source implementation of the Cisco AnyConnnect VPN protocol, which is widely-used in businesses and universities. AnyConnect is a SSL-based VPN protocol that allows individual users to connect to a remote network.

Why Set Up Your Own VPN Server?

Maybe you are a VPN service provider or a system administator, which behooves you to set up our own VPN server.
You don’t trust the no logging policy of VPN service providers, so you go the self-host route.
You can use VPN to implement network security policy. For example, if you run your own email server, you can require users to login only from the IP address of the VPN server by creating an IP address whitelist in the firewall. Thus, your email server is hardened to prevent hacking activities.
Perhaps you are just curious to know how VPN server works.

Features of OpenConnect VPN server

Lightweight and fast. In my test, I can watch YouTube 4K videos with OpenConnect VPN. YouTube is blocked in my country (China).
Runs on Linux and most BSD servers.
Compatible with Cisco AnyConnect client
There are OpenConnect client software for Linux, MacOS, Windows and OpenWRT. For Android and iOS, you can use the Cisco AnyConnect Client.
Supports password authentication and certificate authentication
Supports RADIUS accounting.
Easy to set up

I particularly like that fact that compared to other VPN technologies, it is very easy and convenient for the end-user to use OpenConnect VPN. Whenever I install a Linux distro on my computer and want to quickly unblock websites or hide my IP address, I install OpenConnect client and connect to the server with just two lines of commands:

sudo apt install openconnect

sudo openconnect -b vpn.mydomain.com

There are also OpenConnect VPN client for Fedora, RHEL, CentOS, Arch Linux and OpenSUSE. You can easily install it with your package manager.

sudo dnf install openconnect
sudo yum install openconnect
sudo pacman -S openconnect

Prerequisites

To follow this tutorial, you will need a VPS (Virtual Private Server) that can access blocked websites freely (Outside of your country or Internet filtering system). I recommend Vultr VPS (This is my referral link. You can get $50 free credit by creating an account at Vultr via my referral link). They offer 512M RAM high performance KVM VPS for just $2.5 per month, which is perfect for your private VPN server. Once you have a VPS, install Debian 10 Buster on it and follow the instructions below.

You also need a domain name. I registered my domain name from NameCheap because the price is low and they give whois privacy protection free for life.

Note: The new Vultr $2.5/month plan includes IPv6 address only. You can select the $3.5/month plan at the New York (NJ) data center to have both IPv4 and IPv6 address.

Step 1: Install OpenConnect VPN Server on Debian 10 Buster

Log into your Debian 10 Buster server via SSH. Then use apt to install the ocserv package from Debian repository.

sudo apt update
sudo apt install ocserv

Once installed, the OpenConnect VPN server is automatically started. You can check its status with:

systemctl status ocserv

Sample output:

● ocserv.service - OpenConnect SSL VPN server
   Loaded: loaded (/lib/systemd/system/ocserv.service; enabled; vendor preset: enabled
   Active: active (running) since Thu 2017-11-30 05:45:07 UTC; 11s ago
     Docs: man:ocserv(8)
 Main PID: 19235 (ocserv-main)
   CGroup: /system.slice/ocserv.service
           ├─19235 ocserv-main                                                  
           └─19242 ocserv-secm

Hint: If the above command doesn’t quit immediately, you can press the Q key to gain back control of the terminal.

If it’s not running, then you can start it with:

sudo systemctl start ocserv

By default OpenConnect VPN server listens on TCP and UDP port 443. If it’s being used by web server, then the VPN server can’t be started. We will see how to change the port in OpenConnect VPN configuration file later.

If there’s a firewall running on your server, then you will need to open port 80 and 443. For example, if you use UFW, then run the following commands.

sudo ufw allow 80/tcp
sudo ufw allow 443/tcp

Step 2: Install Let’s Encrypt Client (Certbot) on Debian 10 Buster Server

The gnutls-bin package installed along with ocserv provides tools to create your own CA and server certificate, but we will obtain and install Let’s Encrypt certificate. The advantage of using Let’s Encrypt certificate is that it’s free, easier to set up and trusted by VPN client software.

Run the following commands to install the Let’s Encrypt client (certbot) on Debian 10.

sudo apt install certbot

To check version number, run

certbot --version

Sample output:

certbot 0.31.0

Step 3: Obtain a Trusted TLS Certificate from Let’s Encrypt

I recommend using the standalone or webroot plugin to obtain TLS certificate.

Standalone Plugin

If there’s no web server running on your Debian 10 Buster server and you want OpenConnect VPN server to use port 443, then you can use the standalone plugin to obtain TLS certificate from Let’s Encrypt. Set DNS A record for vpn.yourdomain.com at your domain registrar’s website, then run the following command to obtain certificate.

sudo certbot certonly --standalone --preferred-challenges http --agree-tos --email [email protected] -d vpn.example.com

Explanation:

certonly: Obtain a certificate but don’t install it.
--standalone: Use the standalone plugin to obtain a certificate
--preferred-challenges http: Perform http-01 challenge to validate our domain, which will use port 80.
--agree-tos: Agree to Let’s Encrypt terms of service.
--email: Email address is used for account registration and recovery.
-d: Specify your domain name.

As you can see from the following screenshot, I successfully obtained the certificate.

Using webroot Plugin

If your Debian 10 Buster server has a web server listening on port 80 and 443, then it’s a good idea to use the webroot plugin to obtain a certificate because the webroot plugin works with pretty much every web server and we don’t need to install the certificate in the web server.

First, you need to create a virtual host for vpn.example.com.

Apache

If you are using Apache web server, then create virtual host under /etc/apache2/sites-available/ directory.

sudo nano /etc/apache2/sites-available/vpn.example.com.conf

And paste the following lines into the file.

        
        ServerName vpn.example.com

        DocumentRoot /var/www/ocserv

Save and close the file. Then create the web root directory.

sudo mkdir /var/www/ocserv

Set www-data (Apache user) as the owner of the web root.

sudo chown www-data:www-data /var/www/ocserv -R

Enable this virtual host.

sudo a2ensite vpn.example.com

Reload Apache for the changes to take effect.

sudo systemctl reload apache2

Once virtual host is created and enabled, run the following command to obtain Let’s Encrypt certificate using webroot plugin.

sudo certbot certonly --webroot --agree-tos --email [email protected] -d vpn.example.com -w /var/www/ocserv/

Nginx

If you are using Nginx web server, then create virtual host under /etc/nginx/conf.d/.

sudo nano /etc/nginx/conf.d/vpn.example.com.conf

Paste the following lines into the file.

server {
      listen 80;
      server_name vpn.example.com;

      root /var/www/ocserv/;

      location ~ /.well-known/acme-challenge {
         allow all;
      }
}

Save and close the file. Then create the web root directory.

sudo mkdir /var/www/ocserv

Set www-data (Nginx user) as the owner of the web root.

sudo chown www-data:www-data /var/www/ocserv -R

Reload Nginx for the changes to take effect.

sudo systemctl reload nginx

Once virtual host is created and enabled, run the following command to obtain Let’s Encrypt certificate using webroot plugin.

sudo certbot certonly --webroot --agree-tos --email [email protected] -d vpn.example.com -w /var/www/ocserv/

Step 4: Edit OpenConnect VPN Server Configuration File

Edit ocserv configuration file.

sudo nano /etc/ocserv/ocserv.conf

First, configure password authentication. By default, password authentication through PAM (Pluggable Authentication Modules) is enabled, which allows you to use Debian system accounts to login from VPN clients. This behavior can be disabled by commenting out the following line.

auth = "pam[gid-min=1000]"

If we want users to use separate VPN accounts instead of system accounts to login, we need to add the following line to enable password authentication with a password file.

auth = "plain[passwd=/etc/ocserv/ocpasswd]"

After finishing editing this config file, we will see how to use ocpasswd tool to generate the /etc/ocserv/ocpasswd file, which contains a list of usernames and encoded passwords.

Note: Ocserv supports client certificate authentication, but Let’s Encrypt does not issue client certificate. If you want to enable certificate authentication, you need to set up your own CA to issue client certificate.

Next, if you don’t want ocserv to use TCP and UDP port 443 (there’s a web server using port 443), then find the following two lines and change the port number. Otherwise leave them alone.

tcp-port = 443
udp-port = 443

Then find the following two lines. We need to change them.

server-cert = /etc/ssl/certs/ssl-cert-snakeoil.pem
server-key = /etc/ssl/private/ssl-cert-snakeoil.key

Replace the default setting with the path of Let’s Encrypt server certificate and server key file.

server-cert = /etc/letsencrypt/live/vpn.example.com/fullchain.pem
server-key = /etc/letsencrypt/live/vpn.example.com/privkey.pem

Then, set the maximal number of clients. Default is 128. Set to zero for unlimited.

max-clients = 128

Set the number of devices a user is able to login from at the same time. Default is 2. Set to zero for unlimited.

max-same-clients = 2

Next, find the following line. Change false to true to enable MTU discovery, which can optimize VPN performance.

try-mtu-discovery = false

You can set the time that a client is allowed to stay idle before being connected via the following two parameters. If you prefer the client to stay connected indefinitely, then comment out these two parameters.

idle-timeout=1200
mobile-idle-timeout=1800

After that, set the default domain to vpn.example.com.

default-domain = vpn.example.com

The IPv4 network configuration is as follows by default. This will cause problems because most home routers also set the IPv4 network range to 192.168.1.0/24.

ipv4-network = 192.168.1.0
ipv4-netmask = 255.255.255.0

We can use another private IP address range (such as 10.10.10.0/24) to avoid IP address collision, so change the value of ipv4-network to

ipv4-network = 10.10.10.0

Now uncomment the following line to tunnel all DNS queries via the VPN.

tunnel-all-dns = true

Change DNS resolver address. You can use Google’s public DNS server.

dns = 8.8.8.8
dns = 8.8.4.4

or Cloudflare’s public DNS server.

dns = 1.1.1.1
dns = 1.0.0.1

Note: If you are a VPN service provider, it’s a good practice to run your own DNS resolver. If there’s a DNS resolver running on the same server, then specify the DNS as

dns = 10.10.10.1

10.10.10.1 is the IP address of OpenConnect VPN server in the VPN LAN. This will speed up DNS lookups a little bit for clients because the network latency between the VPN server and the DNS resolver is eliminated.

Then comment out all the route parameters (add # character at the beginning of the following lines), which will set the server as the default gateway for the clients.

#route = 10.0.0.0/8
#route = 172.16.0.0/12
#route = 192.168.0.0/16
#route = fd00::/8
#route = default

#no-route = 192.168.5.0/255.255.255.0

Save and close the file Then restart the VPN server for the changes to take effect.

sudo systemctl restart ocserv

Step 5: Creating VPN Accounts

Now use the ocpasswd tool to generate VPN accounts.

sudo ocpasswd -c /etc/ocserv/ocpasswd username

You will be asked to set a password for the user and the information will be saved to /etc/ocserv/ocpasswd file. To reset password, simply run the above command again.

Step 6: Enable IP Forwarding in Linux Kernel

In order for the VPN server to route packets between VPN client and the Internet, we need to enable IP forwarding. Edit sysctl.conf file.

sudo nano /etc/sysctl.conf

Add the following line at the end of this file.

net.ipv4.ip_forward = 1

Save and close the file. Then apply the changes with the below command. The -p option will load sysctl settings from /etc/sysctl.conf file. This command will preserve our changes across system reboots.

sudo sysctl -p

Step 7: Configure IP Masquerading in Firewall

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:

sudo apt install ufw

First, you need to allow SSH traffic.

sudo ufw allow 22/tcp

Then edit /etc/default/ufw file.

sudo nano /etc/default/ufw

Change the default forward policy from “DROP” to “ACCEPT”.

DEFAULT_FORWARD_POLICY="ACCEPT"

Save and close the file. Next, find the name of your server’s main network interface.

ip addr

As you can see, it’s named ens3 on my Debian server.

To configure IP masquerading, we have to add iptables command in a UFW configuration file.

sudo nano /etc/ufw/before.rules

By default, there are some rules for the filter table. Add the following lines at the end of this file. Replace ens3 with your own network interface name.

# NAT table rules
*nat
:POSTROUTING ACCEPT [0:0]
-A POSTROUTING -o ens3 -j MASQUERADE

# End each table with the 'COMMIT' line or these rules won't be processed
COMMIT

In Nano text editor, you can go to the end of the file by pressing Ctrl W, then pressing Ctrl V.

The above lines will append (-A) a rule to the end of of POSTROUTING chain of 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.

Save and close the file. Then enable UFW.

sudo ufw enable

If you have enabled UFW before, then you can use systemctl to restart UFW.

sudo systemctl restart ufw

Now if you list the rules in the POSTROUTING chain of the NAT table by using the following command:

sudo iptables -t nat -L POSTROUTING

You can see the Masquerade rule.

Step 8: Open Port 443 in Firewall

Run the following command to open TCP and UDP port 443. If you configured a different port for ocserv, then change 443 to your configured port.

sudo ufw allow 443/tcp
sudo ufw allow 443/udp

Now OpenConnect VPN server is ready to accept client connections.

How to Install and Use OpenConnect VPN client on Debian 10 Buster Desktop

Run the following command to install OpenConnect VPN command line client on Debian desktop.

sudo apt install openconnect

You can Connect to VPN from the command line like below. -b flag will make it run in the background after connection is established.

sudo openconnect -b vpn.example.com

By default, openconnect client will contact port 443 of the server. If you configured a different port for the server, then you can add the port number.

sudo openconnect -b vpn.example.com:port-number

You will be asked to enter VPN username and password. If connection is successfully established, you will see the following message.

Got CONNECT response: HTTP/1.1 200 CONNECTED
CSTP connected. DPD 60, Keepalive 300
Connected as 10.10.10.139, using SSL   LZ4, with DTLS   LZ4 in progress
Continuing in background; pid 17050

If the connection failed, you can check the ocserv log to find out why. (Perhaps you didn’t enter the password correctly.)

sudo journaltcl -eu ocserv

To stop the connection, run:

sudo pkill openconnect

To run the client non-interactively, use the following syntax.

echo -n password | sudo openconnect -b vpn.example.com -u username --passwd-on-stdin

If you want to use Network Manager to manage VPN connection, then you need to install these packages.

sudo apt install network-manager-openconnect network-manager-openconnect-gnome

If you are successfully connected to the VPN server, but your public IP address doesn’t change, that’s because IP forwarding or IP masquerading is not working. I once had a typo in my iptables command, which caused my computer not being able to browse the Internet.

Auto-Connect on System Startup

To let OpenConnect VPN client automatically connect to the server at boot time, we can create a systemd service unit.

sudo nano /etc/systemd/system/openconnect.service

Put the following lines to the file. Replace the red text.

[Unit]
  Description=OpenConnect VPN Client
  After=network-online.target
  Wants=network-online.target

[Service]
  Type=simple
  ExecStart=/bin/bash -c '/bin/echo -n password | /usr/sbin/openconnect vpn.example.com -u username --passwd-on-stdin'
  KillSignal=SIGINT
  Restart=always
  RestartSec=2

[Install]
  WantedBy=multi-user.target

Save and close the file. Then enable this service so that it will start at boot time.

sudo systemctl enable openconnect.service

Explanation of the file content:

After=network-online.target and Wants=network-online.target make this service run after network is up.
In reality, this service can still run before network is up. We add Restart=always and RestartSec=2 to restart this service after 2 seconds if this service fails.
Systemd doesn’t recognise pipe redirection. So in the ExecStart directive, we wrap the command in single quotes and run it with the Bash shell.
Since OpenConnect VPN client will run as a systemd service, which runs in the background, there’s no need to add -b flag to the openconnect command.
The KillSignal directive tells Systemd to send the SIGINT signal when the systemctl stop openconnect command is issued. This will performs a clean shutdown by logging the session off, and restoring DNS server settings and the Linux kernel routing table.

To start this Systemd service immediately, run

sudo systemctl start openconnect

To stop this Systemd service, run

sudo systemctl stop openconnect

OpenConnect GUI Client for Windows and MacOS

They can be downloaded from OpenConnect GUI Github Page.

Speed

OpenConnect VPN is pretty fast. I can use it to watch 4k videos on YouTube.

Auto-Renew Let’s Encrypt Certificate

Edit root user’s crontab file.

sudo crontab -e

Add the following line at the end of the file to run the Cron job daily. If the certificate is going to expire in 30 days, certbot will try to renew the certificate. It’s necessary to restart ocserv service for the VPN server to pick up new certificate and key file.

@daily certbot renew --quiet && systemctl restart ocserv

Optimization

OpenConnect by default uses TLS over UDP protocol (DTLS) to achieve faster speed, but UDP can’t provide reliable transmission. TCP is slower than UDP but can provide reliable transmission. One optimization tip I can give you is to disable DTLS, use standard TLS (over TCP), then enable TCP BBR to boost TCP speed.

To disable DTLS, comment out (add # symbol at the beginning) the following line in ocserv configuration file.

udp-port = 443

Save and close the file. Then restart ocserv service.

sudo systemctl restart ocserv.service

To enable TCP BBR, please check out the following tutorial.

How to Easily boost Debian Network Performance by enabling TCP BBR

In my test, standard TLS with TCP BBR enabled is two times faster than DTLS.

Troubleshooting

Note that if you are using OpenVZ VPS, make sure you enable the TUN virtual networking device in VPS control panel. (If you use Vultr VPS, then you have KVM-based VPS, so you don’t have to worry about this.)

If you encounter any problem, then check OpenConnect VPN server log.

sudo journalctl -eu ocserv.service

I found that if I change port 443 to a different port, the great firewall of China will block this VPN connection.

Let OpenConnect VPN server and web server use port 443 at the same time

Normally a port can only be used by one process. However, we can use HAproxy (High Availability Proxy) and SNI (Server Name Indication) to make ocserv and Apache/Nginx use port 443 at the same time.

First, edit ocserv configuration file.

sudo nano /etc/ocserv/ocserv.conf

Uncomment the following line. This will allow ocserv to obtain the client IP address instead of HAproxy IP address.

listen-proxy-proto = true

Then find the following line.

#listen-host = [IP|HOSTNAME]

Change it to

listen-host = 127.0.0.1

This will make ocserv listen on 127.0.0.1 because later HAproxy will need to listen on the public IP address. Save and close the file. Then restart ocserv.

sudo systemctl restart ocserv

Next, we also need to make the web server listen on localhost only, instead of listening on public IP address. If you use Nginx, edit the server block file.

sudo nano /etc/nginx/conf.d/www.example.com.conf

In the SSL server block, find the following directive.

listen 443 ssl;

Change it to

listen 127.0.0.2:443 ssl;

This time we make it listen on 127.0.0.2:443 because 127.0.0.1:443 is already taken by ocserv. Save and close the file. Then restart Nginx.

sudo systemctl restart nginx

Now install HAproxy.

sudo apt install haproxy

Edit configuration file.

sudo nano /etc/haproxy/haproxy.cfg

Copy and paste the following lines to the end of the file. Replace 12.34.56.78 with the public IP address of your server. Replace vpn.example.com with the domain name used by ocserv and www.example.com with the domain name used by your web server.

frontend https
   bind 12.34.56.78:443
   mode tcp
   tcp-request inspect-delay 5s
   tcp-request content accept if { req_ssl_hello_type 1 }

   use_backend ocserv if { req_ssl_sni -i vpn.example.com }
   use_backend nginx if { req_ssl_sni -i www.example.com }
   use_backend nginx if { req_ssl_sni -i example.com }

   default_backend ocserv

backend ocserv
   mode tcp
   option ssl-hello-chk
   server ocserv 127.0.0.1:443 send-proxy-v2

backend nginx
   mode tcp
   option ssl-hello-chk
   server nginx 127.0.0.2:443 check

Save and close the file. Then restart HAproxy.

sudo systemctl restart haproxy

In the configuration above, we utilized the SNI (Server Name Indication) feature in TLS to differentiate VPN traffic and normal HTTPS traffic.

When vpn.example.com is in the TLS Client Hello, HAProxy redirect traffic to the ocserv backend.
When www.example.com is in the TLS Client Hello, HAProxy redirect traffic to the nginx backend.
If the client doesn’t specify the server name in TLS Client Hello, then HAproxy will use the default backend (ocserv).

You can test this setup with the openssl tool. First, run the following command multiple times.

echo | openssl s_client -connect your-server-IP:443 | grep subject

We didn’t specify server name in the above command, so HAproxy will always pass the request to the default backend (ocserv), and its certificate will be sent to the client. Next, run the following two commands.

echo | openssl s_client -servername www.example.com -connect your-server-IP:443 | grep subject

echo | openssl s_client -servername vpn.example.com -connect your-server-IP:443 | grep subject

Now we specified the server name in the commands, so HAproxy will pass request accordingly. Note that the Cisco AnyConnect App doesn’t support TLS SNI, so it’s better to set ocserv as the default backend in HAProxy configuration file.

When renewing Let’s Encrypt certificate for your website, it’s recommended that you use the http-01 chanllenge instead of tls-alpn-01 chanllege, because HAproxy is listening on port 443 of the public IP address, so it can interfere with the renew process.

sudo certbot renew --preferred-challenges http-01

Fixing HAproxy Error

If your Nginx web server doesn’t show up in your browser and you see the following messages in haproxy log (/var/log/haproxy.log)

Server nginx/nginx is DOWN, reason: Socket error, info: "Connection reset by peer

backend nginx has no server available!

Layer6 invalid response

It maybe because your backend Nginx web server is using a TLS certificate with OCSP must staple extension. Nginx doesn’t send the OCSP staple information on the first HTTP request. To make it work, be sure to add a resolver in your Nginx virtual host configuration like below.

{
     ....
     ssl_trusted_certificate /etc/letsencrypt/live/www.example/chain.pem;
     ssl_stapling on;
     ssl_stapling_verify on;

    resolver 8.8.8.8;
    ....
}

Save and close the file. Then restart Nginx.

sudo systemctl restart nginx

Also consider removing health check for the backend server in HAproxy. So change

server nginx 127.0.0.2:443 check

server nginx 127.0.0.2:443

Save and close the file. Then restart HAproxy.

sudo systemctl restart haproxy

Upgrading to the latest version of HAproxy can help too. Previously when I was using HAproxy 1.6 from the default Debian repository, the log file didn’t show much information. To install the latest version, run the following commands:

sudo add-apt-repository ppa:vbernat/haproxy-1.8

sudo apt update

sudo apt install haproxy

How to Disable TLS 1.0 and TLS 1.1 in ocserv

The PCI council deprecated TLS 1.0 in June 30, 2018 and main stream web browsers are going to disable TLS 1.0 and TLS 1.1 in 2020. We should do the same with VPN server. Edit the main configuration file.

sudo nano /etc/ocserv/ocserv.conf

Find the following line:

tls-priorities = "NORMAL:%SERVER_PRECEDENCE:%COMPAT:-RSA:-VERS-SSL3.0:-ARCFOUR-128"

To disable TLS 1.0 and TLS 1.1 in OpenConnect VPN server, just add -VERS-TLS1.0 and -VERS-TLS1.1 in the line.

tls-priorities = "NORMAL:%SERVER_PRECEDENCE:%COMPAT:-RSA:-VERS-SSL3.0:-ARCFOUR-128:-VERS-TLS1.0:-VERS-TLS1.1"

Save and close the file. Then restart ocserv.

sudo systemctl restart ocserv

Now ocserv will only accept TLS 1.2. For further information on configuring the TLS parameter in ocserv, please see GnuTLS priority strings.

To check if TLS 1.0 is supported in your OpenConnect VPN server, run the following command.

openssl s_client -connect vpn.your-domain.com:443 -tls1

And check TLS 1.1

openssl s_client -connect vpn.your-domain.com:443 -tls1_1

If you see the following message in the output, that means the TLS version is not supported.

New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported

Per User or Per Group Configuration

Ocserv allows per user and per group configurations. To enable this feature, uncomment the following two lines in /etc/ocserv/ocserv.conf file.

config-per-user = /etc/ocserv/config-per-user/
config-per-group = /etc/ocserv/config-per-group/

Save and close the file. Then create the per user and per group config directory.

sudo mkdir /etc/ocserv/config-per-user/
sudo mkdir /etc/ocserv/config-per-group/

Next, you can create a file under these two directories. For example, create the user1 file to allow custom configuration for user1.

sudo nano /etc/ocserv/config-per-user/user1

You can also create the group1 file to allow custom configuration for the group named group1.

sudo nano /etc/ocserv/config-per-group/group1

You can add something like below in the file.

route = 10.10.10.0/255.255.255.0

This means that after user1 connect to this VPN server, only traffic to the 10.10.10.0/24 network will be routed via VPN server. Traffic to other IP addresses are routed via the original gateway. I use this to allow my another VPS (virtual private server) to connect to this VPN server.

Save and close the file. Restart ocserv for the changes to take effect.

Wrapping Up

That’s it! I hope this tutorial helped you install and configure OpenConnect VPN on Debian 10 Buster server. As always, if you found this post useful, then subscribe to our free newsletter to get more tips and tricks. Take care 🙂

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Set Up OpenConnect VPN Server (ocserv) on Debian 10 Buster with Let’s Encrypt

Why Set Up Your Own VPN Server?

Features of OpenConnect VPN server

Prerequisites

Step 1: Install OpenConnect VPN Server on Debian 10 Buster

Step 2: Install Let’s Encrypt Client (Certbot) on Debian 10 Buster Server

Step 3: Obtain a Trusted TLS Certificate from Let’s Encrypt

Standalone Plugin

Using webroot Plugin

Apache

Nginx

Step 4: Edit OpenConnect VPN Server Configuration File

Step 5: Creating VPN Accounts

Step 6: Enable IP Forwarding in Linux Kernel

Step 7: Configure IP Masquerading in Firewall

Step 8: Open Port 443 in Firewall

How to Install and Use OpenConnect VPN client on Debian 10 Buster Desktop

Auto-Connect on System Startup

OpenConnect GUI Client for Windows and MacOS

Speed

Auto-Renew Let’s Encrypt Certificate

Optimization

Troubleshooting

Let OpenConnect VPN server and web server use port 443 at the same time

Fixing HAproxy Error

How to Disable TLS 1.0 and TLS 1.1 in ocserv

Per User or Per Group Configuration

Wrapping Up

Other stories

How to Remove (Delete) Directory in Linux

Cp Command in Linux (Copy Files)

Press ESC to close

Why Set Up Your Own VPN Server?

Features of OpenConnect VPN server

Prerequisites

Step 1: Install OpenConnect VPN Server on Debian 10 Buster

Step 2: Install Let’s Encrypt Client (Certbot) on Debian 10 Buster Server

Step 3: Obtain a Trusted TLS Certificate from Let’s Encrypt

Standalone Plugin

Using webroot Plugin

Apache

Nginx

Step 4: Edit OpenConnect VPN Server Configuration File

Step 5: Creating VPN Accounts

Step 6: Enable IP Forwarding in Linux Kernel

Step 7: Configure IP Masquerading in Firewall

Step 8: Open Port 443 in Firewall

How to Install and Use OpenConnect VPN client on Debian 10 Buster Desktop

Auto-Connect on System Startup

OpenConnect GUI Client for Windows and MacOS

Speed

Auto-Renew Let’s Encrypt Certificate

Optimization

Troubleshooting

Let OpenConnect VPN server and web server use port 443 at the same time

Fixing HAproxy Error

How to Disable TLS 1.0 and TLS 1.1 in ocserv

Per User or Per Group Configuration

Wrapping Up

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