Troubleshooting Tip: FortiVoice is not able to join the Security Fabric cause certificate error

FortiVoice is configured to join the Security Fabric root FortiGate.

config system csf
    set status enable
    set upstream-ip 10.22.5.1 <-FortiGate
    set upstream-port 8013
    set configuration-sync local
    set management-ip 10.22.5.6 <-FortiVoice
    set management-port 443
    unset group-name
    unset group-password
end

In the FortiGate, running the csf debug shows the error 'The certificate CN (FortiVoiceEnterprise) doesn't match the serial number'.

diagnose debug application csf  -1
diagnose debug enable

<18823-M> 04 nstd_handle_hello_pkt()-345:
<18823-M> 10000000 nstd_handle_hello_pkt()-387: downstream:10.22.5.6 auth by cert:N
<18823-M> 10000000 nstd_handle_hello_pkt()-401: SN FO100E2TX100000465 copied from hello packet.
<18823-M> 04 nstd_update_fgt_interface()-303:
<18823-M> 800 handle_connection_event_auth_plugin()-3101:
<18823-M> 400 nstd_check_certificate()-2255: The certificate CN (FortiVoiceEnterprise) doesn't match the Serial number (FO100E2TX100000465) sent by 10.22.5.6:52319
<18823-M> 400 handle_connection_event_auth_plugin()-3109: SSL verification for 10.22.5.6:52319 failed.
<18823-M> 40000 nstd_sync_generic_connection_event()-1273:
<18823-M> 100 handle_connection_event_tree_updater()-958:
<18823-M> 04 nstd_downstream_fgt_info_update_fn()-1646:
<18823-M> 08 nstd_downstream_fgt_info_update_fn()-1651: scheduled downstream info updater to run in 3 seconds

The behavior could be matching bug 1084189, where it is described as FortiVoice being unable to join FortiGate fabric root using a certificate-based authentication request method.

This is solved in FortiVoice version 7.2.0. If the behavior remains after the upgrade to this version, open a TAC ticket for further analysis.