Advanced 3CX Academy Study Pack | 2025
Q&A Edition
In the criteria of the "Outbound Rules", "Calls from Extension(s)" having comma separated values will
allow multiple extension ranges to be defined - ✔✔True
The Virtual Extension of the slave must match the master side virtual extension number - ✔✔True
For extensions that are registered over multiple site-to-site VPNs, by default 3CX delivers the audio
between phones if they are on different subnets. - ✔✔False
On outbound calls to external numbers, 3CX will process "Outbound Rules" in a "Best Matching" way,
depending on how many of the criteria match. - ✔✔False
Wireshark can - without any additional Plugins Decode all Codecs including G711A, G711U, GSM, G729,
G726 - ✔✔False
STUN extensions can be configured to connect to the tunnel port of 3CX instead of the SIP port for more
security. - ✔✔False
The log files of 3CX are never cleaned even when you restart the 3CX Services - ✔✔False
Once Secure SIP has been configured in 3CX, Secure SIP certificates will need to be deployed manually in
phones and softphones OS so that they can communicate. - ✔✔False
Remote extensions may be provisioned using the HTTP or HTTPS URLs - ✔✔False
The default Voicemail PIN of an extension consist of 4 random alphanumerical characters. - ✔✔False
, Your 3CX has only one SIP Trunk and receives a call from number 8135791691. If you have a "Inbound
CID Reformatting" rule on the Trunk with "Source Pattern" 813(...)(.*) and "Replace Pattern" \1\2, the
extension that receives the call will see "5791691" as the caller ID on its display. - ✔✔True
When 3CX has been installed without a FQDN from 3CX and in split DNS mode, the DNS server must not
be installed on the same machine as the phone system. - ✔✔True
Your Local IP Phone loses the registration to 3CX and you want do troubleshoot the issue. You should
start a Wireshark Capture on the 3CX Server, reboot the phone, and then apply the Filter
sip.Cseq.Method==REGISTER in order to see if registrations are reaching 3CX - ✔✔True
Your 3CX has only one SIP Trunk and receives a call from number 422033272020 and you want it to be
presented on the extension display as +44272020. You can do this with a "Inbound CID Reformatting"
rule on the Trunk with "Source Pattern" 44(..)(..)(.*) and "Replace Pattern" +44\3. - ✔✔True
When selecting the option "I need a 3CX FQDN" an internal DNS is not mandatory - ✔✔True
The order of "Inbound Rules" is not important when you have DID and CID "Inbound Rules", CIDs always
have higher priority. - ✔✔False
You have a Master Bridge with 3-digit extensions 1xxx and a Slave Bridge with 4-digit extensions 2xxx. In
the "Outbound Rules" you use to rote calls across the bridge, using a prefix is mandatory. - ✔✔False
You have run the 3CX "Firewall Checker" and comes up as Green, but you still have audio issues and calls
dropping on on outbound / inbound calls. Can SIP ALG be the culprit? - ✔✔True
An extension will be allowed up to 25 attempts (default) for authenticating successfully, after what it
will be blacklisted for the default blacklisting interval of 1800 minutes. - ✔✔False
The 3CX SIP port should be filtered by firewall ACL rules to maximize security and allow only trusted IPs
to reach it (VoIP providers or STUN extensions if any). - ✔✔True
Q&A Edition
In the criteria of the "Outbound Rules", "Calls from Extension(s)" having comma separated values will
allow multiple extension ranges to be defined - ✔✔True
The Virtual Extension of the slave must match the master side virtual extension number - ✔✔True
For extensions that are registered over multiple site-to-site VPNs, by default 3CX delivers the audio
between phones if they are on different subnets. - ✔✔False
On outbound calls to external numbers, 3CX will process "Outbound Rules" in a "Best Matching" way,
depending on how many of the criteria match. - ✔✔False
Wireshark can - without any additional Plugins Decode all Codecs including G711A, G711U, GSM, G729,
G726 - ✔✔False
STUN extensions can be configured to connect to the tunnel port of 3CX instead of the SIP port for more
security. - ✔✔False
The log files of 3CX are never cleaned even when you restart the 3CX Services - ✔✔False
Once Secure SIP has been configured in 3CX, Secure SIP certificates will need to be deployed manually in
phones and softphones OS so that they can communicate. - ✔✔False
Remote extensions may be provisioned using the HTTP or HTTPS URLs - ✔✔False
The default Voicemail PIN of an extension consist of 4 random alphanumerical characters. - ✔✔False
, Your 3CX has only one SIP Trunk and receives a call from number 8135791691. If you have a "Inbound
CID Reformatting" rule on the Trunk with "Source Pattern" 813(...)(.*) and "Replace Pattern" \1\2, the
extension that receives the call will see "5791691" as the caller ID on its display. - ✔✔True
When 3CX has been installed without a FQDN from 3CX and in split DNS mode, the DNS server must not
be installed on the same machine as the phone system. - ✔✔True
Your Local IP Phone loses the registration to 3CX and you want do troubleshoot the issue. You should
start a Wireshark Capture on the 3CX Server, reboot the phone, and then apply the Filter
sip.Cseq.Method==REGISTER in order to see if registrations are reaching 3CX - ✔✔True
Your 3CX has only one SIP Trunk and receives a call from number 422033272020 and you want it to be
presented on the extension display as +44272020. You can do this with a "Inbound CID Reformatting"
rule on the Trunk with "Source Pattern" 44(..)(..)(.*) and "Replace Pattern" +44\3. - ✔✔True
When selecting the option "I need a 3CX FQDN" an internal DNS is not mandatory - ✔✔True
The order of "Inbound Rules" is not important when you have DID and CID "Inbound Rules", CIDs always
have higher priority. - ✔✔False
You have a Master Bridge with 3-digit extensions 1xxx and a Slave Bridge with 4-digit extensions 2xxx. In
the "Outbound Rules" you use to rote calls across the bridge, using a prefix is mandatory. - ✔✔False
You have run the 3CX "Firewall Checker" and comes up as Green, but you still have audio issues and calls
dropping on on outbound / inbound calls. Can SIP ALG be the culprit? - ✔✔True
An extension will be allowed up to 25 attempts (default) for authenticating successfully, after what it
will be blacklisted for the default blacklisting interval of 1800 minutes. - ✔✔False
The 3CX SIP port should be filtered by firewall ACL rules to maximize security and allow only trusted IPs
to reach it (VoIP providers or STUN extensions if any). - ✔✔True
