I have configured SSL/TLS on Db2/Linux v11.5.7.0. In DBeaver 22.1.5 (Java GUI program to access database) in Driver properties I have configured parameter: sslConnection to true and DBeaver successfully connects to Db2 user using SSL/TLS.

According to Db2 Java Driver documentation in DBeaver at Driver properties I have configured sslClientHostnameValidation to BASIC to enable Db2 client to execute hostname validation.

When I double click to establish connection in DBeaver I get error:

[jcc][t4][20162][14259][4.31.10] Connection failed: could not establish a SSL connection with the server. The connection has been configured to use hostname validation and the servers TLS certificate does not contain a hostname or IP address which matches the value configured by the client. ERRORCODE=-20576, SQLSTATE=08001

To troubleshoot the problem, in DBeaver I enabled Connection calls trace and the output is:

[jcc][Time:2022-09-01-13:32:11.588][Thread:Connect to 'test1ssl_hostname_validation'][Connection@1fcbbce6]doHostnameValidation () called [jcc][Time:2022-09-01-13:32:11.588][Thread:Connect to 'test1ssl_hostname_validation'][Connection@1fcbbce6]doHostnameValidation () returned sslIsHostnameValid=false

It does not tell anything about what was the hostname it checked.

I have read Db2 documentation Troubleshooting hostname validation at the client when negotiating a TLS connection and according to documentation error should be logged into db2diag.log at Db2 server site. But there is no error at all recorded in my case.

I have even increased DIAGLEVEL dbm cfg parameter to maximum 4 and restarted the instance, reproduced the problem, but still no error is displayed in db2diag.log

For certificate I have double check Subject Alternative Name and there is correctly set FQDN.

How can I verify which hostname did client recognized and which hostname did it get from certificate? Regards

  • Try both forward and reverse name resolution from the client: they should both yield the same hostname, and that hostname must be present in the server certificate.
    – mustaccio
    Sep 2, 2022 at 11:48

1 Answer 1


From CONNECT trace I have found out that serverName was set to localhost instead of server name.

  1. Right click on connection and select Edit Connection.
  2. Make sure Connection setting | Main tab | Database section | Host field has the same value as SSL certificate's:
  • Subject Alternative Name and/or
  • Subject/CN value

Because my Db2 server is running inside VirtualBox machine accessed using Port Forwarding I solved the problem:

  1. In DBeaver at Connection Settings | Main tab | Host field I have set my server name FQDM.
  2. In C:\Windows\system32\drivers\etc\hosts file I have added new line starting with set: then space and my server's FQDM.
  3. In DBeaver connect and connect is successful.

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