3CX ACADEMY, ADVANCED
CERTIFICATION QUESTIONS AND
ANSWERS
In43the43criteria43of43the43"Outbound43Rules",43"Calls43from43Extension(s)"43having43com
ma43separated43values43will43allow43multiple43extension43ranges43to43be43defined43-
43answer--True
The43Virtual43Extension43of43the43slave43must43match43the43master43side43virtual43exten
sion43number43-43answer--True
For43extensions43that43are43registered43over43multiple43site-to-
site43VPNs,43by43default433CX43delivers43the43audio43between43phones43if43they43are43o
n43different43subnets.43-43answer--False
On43outbound43calls43to43external43numbers,433CX43will43process43"Outbound43Rules"43i
n43a43"Best43Matching"43way,43depending43on43how43many43of43the43criteria43match.43-
43answer--False
Wireshark43can43-
43without43any43additional43Plugins43Decode43all43Codecs43including43G711A,43G711U,4
3GSM,43G729,43G72643-43answer--False
STUN43extensions43can43be43configured43to43connect43to43the43tunnel43port43of433CX43i
nstead43of43the43SIP43port43for43more43security.43-43answer--False
The43log43files43of433CX43are43never43cleaned43even43when43you43restart43the433CX43S
ervices43-43answer--False
Once43Secure43SIP43has43been43configured43in433CX,43Secure43SIP43certificates43will43
need43to43be43deployed43manually43in43phones43and43softphones43OS43so43that43they43
can43communicate.43-43answer--False
Remote43extensions43may43be43provisioned43using43the43HTTP43or43HTTPS43URLs43-
43answer--False
, The43default43Voicemail43PIN43of43an43extension43consist43of43443random43alphanumeri
cal43characters.43-43answer--False
Your433CX43has43only43one43SIP43Trunk43and43receives43a43call43from43number4381357
91691.43If43you43have43a43"Inbound43CID43Reformatting"43rule43on43the43Trunk43with43"S
ource43Pattern"43813(...)
(.*)43and43"Replace43Pattern"43\1\2,43the43extension43that43receives43the43call43will43see4
3"5791691"43as43the43caller43ID43on43its43display.43-43answer--True
When433CX43has43been43installed43without43a43FQDN43from433CX43and43in43split43DNS4
3mode,43the43DNS43server43must43not43be43installed43on43the43same43machine43as43the4
3phone43system.43-43answer--True
Your43Local43IP43Phone43loses43the43registration43to433CX43and43you43want43do43troubl
eshoot43the43issue.43You43should43start43a43Wireshark43Capture43on43the433CX43Server,
43reboot43the43phone,43and43then43apply43the43Filter43sip.Cseq.Method==REGISTER 43in
43order43to43see43if43registrations43are43reaching433CX43-43answer--True
Your433CX43has43only43one43SIP43Trunk43and43receives43a43call43from43number4342203
327202043and43you43want43it43to43be43presented43on43the43extension43display43as43+44
272020.43You43can43do43this43with43a43"Inbound43CID43Reformatting"43rule43on43the43Tr
unk43with43"Source43Pattern"4344(..)(..)(.*)43and43"Replace43Pattern"43+44\3.43-
43answer--True
When43selecting43the43option43"I43need43a433CX43FQDN"43an43internal43DNS43is43not43
mandatory43-43answer--True
The43order43of43"Inbound43Rules"43is43not43important43when43you43have43DID43and43CID
43"Inbound43Rules",43CIDs43always43have43higher43priority.43-43answer--False
You43have43a43Master43Bridge43with433-
digit43extensions431xxx43and43a43Slave43Bridge43with434-
digit43extensions432xxx.43In43the43"Outbound43Rules"43you43use43to43rote43calls43across4
3the43bridge,43using43a43prefix43is43mandatory.43-43answer--False
You43have43run43the433CX43"Firewall43Checker"43and43comes43up43as43Green,43but43yo
u43still43have43audio43issues43and43calls43dropping43on43on43outbound43/43inbound43calls
.43Can43SIP43ALG43be43the43culprit?43-43answer--True
An43extension43will43be43allowed43up43to432543attempts43(default)43for43authenticating43s
uccessfully,43after43what43it43will43be43blacklisted43for43the43default43blacklisting43interval
43of43180043minutes.43-43answer--False
CERTIFICATION QUESTIONS AND
ANSWERS
In43the43criteria43of43the43"Outbound43Rules",43"Calls43from43Extension(s)"43having43com
ma43separated43values43will43allow43multiple43extension43ranges43to43be43defined43-
43answer--True
The43Virtual43Extension43of43the43slave43must43match43the43master43side43virtual43exten
sion43number43-43answer--True
For43extensions43that43are43registered43over43multiple43site-to-
site43VPNs,43by43default433CX43delivers43the43audio43between43phones43if43they43are43o
n43different43subnets.43-43answer--False
On43outbound43calls43to43external43numbers,433CX43will43process43"Outbound43Rules"43i
n43a43"Best43Matching"43way,43depending43on43how43many43of43the43criteria43match.43-
43answer--False
Wireshark43can43-
43without43any43additional43Plugins43Decode43all43Codecs43including43G711A,43G711U,4
3GSM,43G729,43G72643-43answer--False
STUN43extensions43can43be43configured43to43connect43to43the43tunnel43port43of433CX43i
nstead43of43the43SIP43port43for43more43security.43-43answer--False
The43log43files43of433CX43are43never43cleaned43even43when43you43restart43the433CX43S
ervices43-43answer--False
Once43Secure43SIP43has43been43configured43in433CX,43Secure43SIP43certificates43will43
need43to43be43deployed43manually43in43phones43and43softphones43OS43so43that43they43
can43communicate.43-43answer--False
Remote43extensions43may43be43provisioned43using43the43HTTP43or43HTTPS43URLs43-
43answer--False
, The43default43Voicemail43PIN43of43an43extension43consist43of43443random43alphanumeri
cal43characters.43-43answer--False
Your433CX43has43only43one43SIP43Trunk43and43receives43a43call43from43number4381357
91691.43If43you43have43a43"Inbound43CID43Reformatting"43rule43on43the43Trunk43with43"S
ource43Pattern"43813(...)
(.*)43and43"Replace43Pattern"43\1\2,43the43extension43that43receives43the43call43will43see4
3"5791691"43as43the43caller43ID43on43its43display.43-43answer--True
When433CX43has43been43installed43without43a43FQDN43from433CX43and43in43split43DNS4
3mode,43the43DNS43server43must43not43be43installed43on43the43same43machine43as43the4
3phone43system.43-43answer--True
Your43Local43IP43Phone43loses43the43registration43to433CX43and43you43want43do43troubl
eshoot43the43issue.43You43should43start43a43Wireshark43Capture43on43the433CX43Server,
43reboot43the43phone,43and43then43apply43the43Filter43sip.Cseq.Method==REGISTER 43in
43order43to43see43if43registrations43are43reaching433CX43-43answer--True
Your433CX43has43only43one43SIP43Trunk43and43receives43a43call43from43number4342203
327202043and43you43want43it43to43be43presented43on43the43extension43display43as43+44
272020.43You43can43do43this43with43a43"Inbound43CID43Reformatting"43rule43on43the43Tr
unk43with43"Source43Pattern"4344(..)(..)(.*)43and43"Replace43Pattern"43+44\3.43-
43answer--True
When43selecting43the43option43"I43need43a433CX43FQDN"43an43internal43DNS43is43not43
mandatory43-43answer--True
The43order43of43"Inbound43Rules"43is43not43important43when43you43have43DID43and43CID
43"Inbound43Rules",43CIDs43always43have43higher43priority.43-43answer--False
You43have43a43Master43Bridge43with433-
digit43extensions431xxx43and43a43Slave43Bridge43with434-
digit43extensions432xxx.43In43the43"Outbound43Rules"43you43use43to43rote43calls43across4
3the43bridge,43using43a43prefix43is43mandatory.43-43answer--False
You43have43run43the433CX43"Firewall43Checker"43and43comes43up43as43Green,43but43yo
u43still43have43audio43issues43and43calls43dropping43on43on43outbound43/43inbound43calls
.43Can43SIP43ALG43be43the43culprit?43-43answer--True
An43extension43will43be43allowed43up43to432543attempts43(default)43for43authenticating43s
uccessfully,43after43what43it43will43be43blacklisted43for43the43default43blacklisting43interval
43of43180043minutes.43-43answer--False
