The Client Log Contains "Options error: Unrecognized option or missing or extra parameter(s) in XXX: disable-dco"

Applicable Client

Linux

Symptom

A client cannot connect to a P2C VPN gateway, and the log contains the following error information:

Options error: Unrecognized option or missing or extra parameter(s) in XXX: disable-dco

Possible Causes

The OpenVPN client software version is 2.5 or earlier, which cannot identify the disable-dco configuration item.

Procedure

1. On Windows, open the client_config.conf file using Notepad or Notepad++.
2. Comment out disable-dco.
   1. Press Ctrl+F to search for and locate disable-dco.
   2. Enter # in front of the line where disable-dco is located to comment out the line.

      ...
      ...
      # disable-dco
      ...
      ...

3. Save the .conf configuration file.
4. Upload the .conf configuration file to the Linux operating system using Xftp. In this example, the file is uploaded to the /opt/ directory.
5. On Linux, run the following command to go to the directory where the client configuration file is stored:

   cd /opt/

6. Run the following command to start the OpenVPN client and connect to the VPN gateway:

   openvpn --config /opt/openvpn_config_user-01.conf

   If the following information in bold is displayed, the OpenVPN connection is successfully established:

   2025-02-27 19:22:41 Note: Kernel support for ovpn-dco missing, disabling data channel offload.
   2025-02-27 19:22:41 OpenVPN 2.6.12 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] [DCO]
   2025-02-27 19:22:41 library versions: OpenSSL 3.3.1 4 Jun 2024, LZO 2.10
   ...
   ...
   ...
   2025-02-27 19:22:42 Initialization Sequence Completed
   ...
   ...

7. 

   XX.XX.XX.XX indicates the private IP address of the ECS to be connected. Replace it with the actual private IP address.

   If information similar to the following is displayed, the client can communicate with the ECS:

   64 bytes from XX.XX.XX.XX: icmp_seq=1 ttl=63 time=1.27 ms
   64 bytes from XX.XX.XX.XX: icmp_seq=2 ttl=63 time=1.36 ms
   64 bytes from XX.XX.XX.XX: icmp_seq=3 ttl=63 time=1.40 ms
   64 bytes from XX.XX.XX.XX: icmp_seq=4 ttl=63 time=1.29 ms
   64 bytes from XX.XX.XX.XX: icmp_seq=5 ttl=63 time=1.35 ms
   64 bytes from XX.XX.XX.XX: icmp_seq=6 ttl=63 time=1.52 ms