Thanks all for your answers ans suggestions. It cannot be a fail2ban problem as firewall was disabled on the server for the tests. The time was playing against me so I went back to centos6 (these desktops must be available monday) and all run fine. I will investigate this later. It's easy for me to switch from Centos6 to Centos7 as the OS is automatically installed (PXE boot + Kickstart) Patrick