Set Up OpenConnect VPN Server (ocserv) on Debian 11 Bullseye

This tutorial is going to show you how to run your own VPN server by installing OpenConnect VPN server on Debian 11 Bullseye. 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 an 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 administrator, which behooves you to set up your 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 log in 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.

OpenConnect VPN Server (ocserv) on Debian 11 Bullseye

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 is 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 for system administrators
  • Easy setup process for end-users.
  • OpenConnect VPN can be configured to operate on TCP port 443 and uses standard TLS protocol to encrypt network traffic. It looks like standard HTTPS protocol, which makes it hard to be blocked.

I particularly like the 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

There is 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


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 Kamatera VPS, which features:

  • 30 days free trial.
  • Starts at $4/month (1GB RAM)
  • High-performance KVM-based VPS
  • 9 data centers around the world, including United States, Canada, UK, Germany, The Netherlands, Hong Kong, and Isreal.

Follow the tutorial linked below to create your Linux VPS server at Kamatera.

Once you have a VPS running Debian 11 Bullseye, follow the instructions below.

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

Step 1: Install OpenConnect VPN Server on Debian 11 Bullseye

Log into your Debian 11 Bullseye 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 Sat 2021-09-25 21:35:29 EDT; 8s ago
       Docs: man:ocserv(8)
   Main PID: 52509 (ocserv-main)
      Tasks: 2 (limit: 1095)
     Memory: 2.0M
        CPU: 12ms
     CGroup: /system.slice/ocserv.service
             ├─52509 ocserv-main
             └─52519 ocserv-sm

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 port 443 is being used by a web server, then the VPN server might not be able to start. We will see how to change the port in OpenConnect VPN configuration file later.

Step 2: Install UFW Firewall

There are several firewall solutions available for Linux. I will use UFW, which is a front end to the iptables firewall and is easy to manage. Install UFW on Debian with:

sudo apt install ufw

First, you need to allow SSH traffic.

sudo ufw allow 22/tcp

Then you need to open TCP port 80 and 443.

sudo ufw allow 80,443/tcp

Next, enable UFW.

sudo ufw enable

Step 3: Install Let’s Encrypt Client (Certbot) on Debian 11 Bullseye 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 11.

sudo apt install certbot

To check version number, run

certbot --version

Sample output:

certbot 1.12.0

Step 4: Obtain a Trusted TLS Certificate from Let’s Encrypt

You can use the standalone, apache, or nginx plugin to obtain TLS certificate. In the following texts, you should replace with your real domain name.

Standalone Plugin

If there’s no web server running on your Debian 11 Bullseye 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 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


  • 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.


If you encounter the following error, it means there’s a web server that’s already using port 80, so you should use the webroot plugin to obtain TLS certificate.

Problem binding to port 80: Could not bind to IPv4 or IPv6.

Using webroot Plugin

If your Debian 11 Bullseye 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


If you are using Apache web server, then you need to install the Certbot Apache plugin.

sudo apt install python3-certbot-apache

Create virtual host under /etc/apache2/sites-available/ directory.

sudo nano /etc/apache2/sites-available/

And paste the following lines into the file.

<VirtualHost *:80>        

        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

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 apache plugin.

sudo certbot certonly -a apache --agree-tos --email [email protected] -d


If you are using Nginx web server, then you need to install the Certbot Nginx plugin.

sudo apt install python3-certbot-nginx

create virtual host under /etc/nginx/conf.d/.

sudo nano /etc/nginx/conf.d/

Paste the following lines into the file.

server {
      listen 80;

      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 Certbot Nginx plugin.

sudo certbot certonly -a nginx --agree-tos --email [email protected] -d

Step 5: Edit OpenConnect VPN Server Configuration File

Edit ocserv configuration file.

sudo nano /etc/ocserv/ocserv.conf

First, we need to configure password authentication. By default, password authentication through PAM (Pluggable Authentication Modules) is enabled, which allows you to use Debian system accounts to log in 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]"

In step 6, we will use the 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, find the following two lines.

tcp-port = 443
udp-port = 443

Comment out the UDP port. (We will use TCP BBR algorithm to boost TCP speed.)

tcp-port = 443 
#udp-port = 443

If you don’t want ocserv to use TCP port 443 (there’s a web server using port 443?), then change the TCP port number. Otherwise leave it alone.

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/
server-key = /etc/letsencrypt/live/

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

By default, keepalive packets are sent every 300 seconds (5 minutes). I prefer to use a short time (30 seconds) to reduce the chance of VPN connection dropout.

keepalive = 30

Next, find the following line. Change false to true to enable MTU discovery.

try-mtu-discovery = false

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


After that, set the default domain to

default-domain =

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

ipv4-network =
ipv4-netmask =

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

ipv4-network =

Find the following two lines and uncomment them, so VPN clients will be given private IPv6 addresses.

ipv6-network = fda9:4efe:7e3b:03ea::/48
ipv6-subnet-prefix = 64

If you see the following line

ipv6-network = fda9:4efe:7e3b:03ea::/64

Please change it to:

ipv6-network = fda9:4efe:7e3b:03ea::/48

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

tunnel-all-dns = true

By default, ocserv uses (Google) and (Cloudflare) public DNS servers, which is fine.

dns =
dns =

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 = 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 =
#route =
#route =
#route = fd00::/8
#route = default

#no-route =

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

sudo systemctl restart ocserv

Step 6: 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 7: Enable IP Forwarding in Linux Kernel

In order for the VPN server to route packets between VPN clients and the Internet, we need to enable IP forwarding by running the following command.

echo "net.ipv4.ip_forward = 1" | sudo tee /etc/sysctl.d/60-custom.conf

Also, run the following two commands to enable TCP BBR algorithm to boost TCP speed.

echo "net.core.default_qdisc=fq" | sudo tee -a /etc/sysctl.d/60-custom.conf

echo "net.ipv4.tcp_congestion_control=bbr" | sudo tee -a /etc/sysctl.d/60-custom.conf

Then apply the changes with the below command. The -p option will load sysctl settings from /etc/sysctl.d/60-custom.conf file. This command will preserve our changes across system reboots.

sudo sysctl -p /etc/sysctl.d/60-custom.conf

Step 8: 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. Find the name of your server’s main network interface.

ip -c a

As you can see, it’s named eth0 on my Debian server.

ocserv debian 11 bullseye

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

# NAT table rules

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

Replace eth0 with your own network interface name.


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.

By default, UFW forbids packet forwarding. We can allow forwarding for our private network. Find the ufw-before-forward chain in this file and add the following 3 lines, which will accept packet forwarding if the source IP or destination IP is in the range.

# allow forwarding for trusted network
-A ufw-before-forward -s -j ACCEPT
-A ufw-before-forward -d -j ACCEPT

ufw allow packet fowarding

Save and close the file. Then 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.


It can take some time for UFW to process the firewall rules. If the masquerade rule doesn’t show up, then restart UFW again (sudo systemctl restart ufw).

Step 9: 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.

For those of you who run a local DNS resolver, if you specified as the DNS server for VPN clients, then you must allow VPN clients to connect to port 53 with the following UFW rule.

sudo ufw insert 1 allow in from

You also need to edit the BIND DNS server’s configuration to allow VPN clients to send recursive DNS queries like below.

allow-recursion {;; };

OpenConnect GUI Client for Windows and macOS

They can be downloaded from OpenConnect GUI Github Page.

How to Install and Use OpenConnect VPN client on Debian 11 Bullseye 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

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

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, 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 -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.

  Description=OpenConnect VPN Client

  ExecStart=/bin/bash -c '/bin/echo -n password | /usr/sbin/openconnect -u username --passwd-on-stdin'


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:

  • and 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

Automatic-Restart When VPN Connection Drops

Sometimes the VPN connection would drop due to various reasons. To make the VPN client automatically restart, edit the root user’s crontab file.

sudo crontab -e

Add the following line at the end of this file.

* * * * * ping -c 10 > /dev/null || systemctl restart openconnect

This Cron job will run every minute to check if the VPN client can ping the VPN server’s private IP address ( If the ping is unsuccessful, then the command on the right will be executed to restart the VPN client. || is the OR operator in Bash. It executes the command on the right only if the command on the left returned an error.

Save and close the file.


OpenConnect VPN is pretty fast. I can use it to watch 4k videos on YouTube. As you can see, the connection speed is 63356 Kbps, which translates to 61 Mbit/s.

ocserv vpn speed test singapore server

And here’s the test results on

ocserv vpn speed test singapore

Speed 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. Note that you need to disable DTLS in ocserv, or TCP BBR won’t work.

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

Another very important factor affecting speed is how good the connection between your local computer and the VPN server is. If you live in the middle east and the VPN server is located in the U.S, the speed would be slow. Choose a data center that’s close to where you live.

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

Troubleshooting Tips


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

Log File

If you encounter any problems, 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.

Debugging Mode

If ocserv tells you that it can’t load the /etc/ocserv/ocserv.conf file, you can stop ocserv.

sudo systemctl stop ocserv

Then run it in the foreground with debugging enabled.

sudo /usr/sbin/ocserv --foreground --pid-file /run/ --config /etc/ocserv/ocserv.conf --debug=10

Then output might give you some clues why ocserv isn’t working.

Can’t browse the Internet

If you are successfully connected to the VPN server, but you can’t browse the Internet, that’s because IP forwarding or IP masquerading is not working. I remember my VPS provider once did a platform upgrade, which changed the name of the main network interface from ens3 to enp3s0, so I had to update the name in the UFW file (/etc/ufw/before.rules).

Syntax Error

If you see the following error when trying to establish VPN connection, it’s probably because there’s a syntax error in your ocserv config file. Check the journal (sudo journalctl -eu ocserv) to find out.

Got inappropriate HTTP CONNECT response: HTTP/1.1 401 Cookie is not acceptable

Restart Your Computer

If you see the following error when trying to establish VPN connection, it’s likely a local computer problem. Try restarting your computer.

Server '' requested Basic authentication which is disabled by default

TLS connection was non-properly terminated

If you see the following error on the client when trying to establish a VPN connection,

SSL connection failure: The TLS connection was non-properly terminated.

you probably should restart the ocserv service on the VPN server.

sudo systemctl restart ocserv

You can create a cron job to automatically restart ocserv once per day at 4 AM.

sudo crontab -e

Add the following line.

0 4 * * * systemctl restart ocserv

Save and close the file.

The local network may not be trustworthy

If you use the Cisco AnyConnect VPN client on iOS, and you encounter the following error, it’s likely your TLS certificate has expired.

cisco secure client cannot confirm it is connected to your secure gateway

If the TLS certificate has expired, you will also see the following error when trying to establish a VPN connection on a Linux desktop.

Server certificate verify failed: certificate expired
Certificate from VPN server "" failed verification.
Reason: certificate expired
To trust this server in future, perhaps add this to your command line:
     --servercert pin-sha256:er1Kv/37ZxHpN6VESmYVS7vw4wXEB1oYELwiBS2wcvc=
Enter 'yes' to accept, 'no' to abort; anything else to view: fgets (stdin): Operation now in progress

You will need to run the following command to renew TLS certificate.

sudo certbot renew --quiet

Don’t forget to restart ocserv.

sudo systemctl restart ocserv

If this error still persists after renewing the certificate, be sure to check the server-cert and server-key parameter in the /etc/ocserv/ocserv.conf file. Maybe it’s pointed to the wrong file.

No Tap-Windows Adapter installed on this system

If you use the OpenConnect GUI Windows client and found the “No Tap-Windows Adapter installed on this system” error in the logs (View – Log Window), this is likely because you have install other VPN clients afterward like OpenVPN.

To fix this error, you need to uninstall OpenConnect GUI client and reinstall it. In the setup wizard, you will have the option to install the TAP driver.

openconnect windows tap driver

Make OpenConnect VPN Server and Web Server Use Port 443 at the Same Time

Please read the following article:

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:


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.


Save and close the file. Then restart ocserv.

sudo systemctl restart ocserv

Now ocserv will only accept TLS 1.3 and 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 -tls1

And check TLS 1.1

openssl s_client -connect -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/ /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 =

This means that after user1 connect to this VPN server, only traffic to the network will be routed via the VPN server. Traffic to other IP addresses is routed via the original gateway. This is known as split tunneling, which is useful when:

  • You just want the VPN clients to be able to browse internal resources and don’t want all the traffic to go through the VPN server.
  • You need to build a private network for cloud servers.
  • The client needs to connect to multiple VPNs. One VPN could use split tunneling and the other use a full tunnel.

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 11 Bullseye 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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13 Responses to “Set Up OpenConnect VPN Server (ocserv) on Debian 11 Bullseye

  • Robert Huang
    2 years ago

    Hi There,

    Your post is very helpful. Thank you.

    I have a question and hopefully you can answer. I have a Debian 11 in Oracle Cloud. The UFW is not loaded. In my case, How can I build a ocserv server accordingly? Thanks again.


    root@debian:~# ufw status
    -bash: ufw: command not found
    root@debian:~# systemctl status ufw
    Unit ufw.service could not be found.
    root@debian:~# ip ad
    1: lo:  mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
        link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
        inet scope host lo
           valid_lft forever preferred_lft forever
        inet6 ::1/128 scope host
           valid_lft forever preferred_lft forever
    2: ens3:  mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
        link/ether 02:00:17:00:f9:42 brd ff:ff:ff:ff:ff:ff
        altname enp0s3
        inet brd scope global ens3
           valid_lft forever preferred_lft forever
        inet6 fe80::17ff:fe00:f942/64 scope link
           valid_lft forever preferred_lft forever
    • Xiao Guoan (Admin)
      2 years ago

      sudo apt install ufw

      • Robert Huang
        2 years ago

        My bad. I didn’t make myself clear.

        What I’m asking is, your solution won’t work if ufw is not installed. Am I right?

        Thanks again.

      • sadegh
        1 year ago

        i config according to the passage.
        client connected but speed very slow and ping have very time out

    • Xiao Guoan (Admin)
      2 years ago

      If you don’t use UFW, you can still make it work by converting UFW rule to iptables rule.

      • Robert Huang
        2 years ago

        Thanks for the explanation. It looks like I need to install UFW or iptables or nftables to make it work.

  • Hi is it possible to add instructions how to configure HMAC-based one-time password (HOTP)

  • I wanna see if there is a way to relay ocserv between 2 regional servers? For example I will have a server in Shenzhen and another server in US-West1, and relay connections (encryption) by settings up ocserv on both ends?


  • Is there any nagios plugin, to check de ocserv status and occtl info?

  • Hi, thank you for this amazing post. From the beginning, when I use `systemctl status ocserv` I see different red lines at the bottom (probably errors), though it’s running and it’s green.

    For example:

    GnuTLS error (at worker-vpn.c:861): The TLS connection was non-properly terminated.


    error connecting to sec-mod socket ‘/run/ocserv.socket.a1c0b506’: No such file or directory

    I wish you could continue it with a second post, explaning the odds and bugs and how we can solve them.

  • For me, the `iptables -t nat -L POSTROUTING` command does not show anything. Even after multiple restart of the ufw and waiting.

  • Stellar
    1 year ago

    Hello there

    Thank you for the easy tutorial.
    I configured 2 servers with this and they are both working fine with my wifi connection (different data centers)
    I have problem making it work on mobile data. It is probably a carrier problem but I cannot figure out what they did and how I can get over it. vpn connects normally with data transfer(according to openconnect on my phone)
    But there is no internet. I tried pinging the server local ip (gateway) after the vpn connects, right after it connects it gives me a very weak reply with 2000+ ms. but time outs after that.

    Anyone has a suggestions ?

    I was thinking maybe it is the port. but I don’t want to change the port and make the government firewall sensitive to my ip (maybe).

  • Latency is high after some time in OCSERV server; we are using Digitalocean

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