3CX PBX does not reply on option query

[jjvalstar]

Could someone explain me why my 3CX PBX server does not response on an option query (see below)
I used wireshark and filtered on SIP messages.

OPTIONS sip:87.195.251.196 SIP/2.0
Via: SIP/2.0/UDP MonitisDE:37515;rport
From: sip:checksip@MonitisDE:37515;tag=ah9cv5
To: sip:87.195.251.196
Call-ID: lvtv8l@MonitisDE
CSeq: 1 OPTIONS
Contact: sip:checksip@MonitisDE:37515
Content-length: 0
Max-Forwards: 100
User-agent: check_sip 1.02
Accept: application/sdp

The above message is filtered on my 3CX PBX server, I only see the message coming in and no response going out from the 3CX.

 

[IPAlarms]

Not all SIP servers respond to OPTIONS requests. I cannot confirm whether or not 3CX can be setup to respond, so hopefully someone will be along later to let you know.

 

[lneblett]

You may want to check the how and to what the message was sent.

Is the server behind a firewall? Are you sending the message to port 5060 which is the SIP listener/server port?

 

[ian.watts]

I had an ISP/ITSP poo-poo their firewall until we set up a multi-homed config on the PBX machine, bypassing the firewall.

My contact reported it has been fine since, whereas before the conference calls would get hung up by the ITSP because there was no OPTIONS response. I never fired up Wireshark to see if their allegations were solid or not.. and counterargued that the firewall would have issues with other SIP verbs like INVITE,BYE, etc.. as well as the responses of 487,200,180.. would also "not" make it back.. the firewall is Layer 3.. not Layer 7.

They said they were compatible with 3CX.. we have our doubts to the extent that if it were our call, we'd go with a different SIP trunk provider and frankly wouldn't ever recommend that ISP for VOIP at all.. but the response 3CX is issuing may be problematic when behind a firewall for a provider who needs a proper response.. I just haven't bothered to Wireshark the thing to find out.

Maybe it's time.