The article provides details what messages are seen on device when TACACS doesn't work and details to check

TACACs is not working on the device and we will see below error messages ,

June 09 10:50:03.502 2025 QFX1 sshd: PAM_TACPLUS_SEND_AUTHEN_FAIL: Failed in sending authentication with error Network read timed out.

• There errors will occur if the device is unable to read the authentication response from the Tacplus server for the authentication request it has sent.
• Kindly make sure the secret passwords used are same on both device and server
• Check for the connectivity from the local device to the TACAS server, make sure there are no firewall blocking the reachability
• TACACS usually uses port 49, so make sure the port is open on both the device and and the TACACS server.
• Also to troubleshoot we can take pcaps on the em0 of QFX and tcp dump on the TACACS server