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3CX On Prem VMWare Appliance - no inbound calls

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Sean Glasspool

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Hello!

Been banging my head on this one for a couple of days. I am quite well versed in the technologies being used here so this is my senario, and I am hoping for some assistance as per the title.

  • 3CX Debian based appliance installed in VMWare
  • Everything works perfectly with the exeption the PBX will not accept any inbound SIP calls.
  • Using on prem as the customer has a large number of legacy SPA504G phones that will only register on a LAN.
  • Microtik Rb2011 with latest firmware and respective NAT rules in place.
  • All firewall tests in 3CX pass fine.
  • Tested SIP trunk against one of our VPS based instances and works fine.
  • Outbound calls from the on prem instance works.
  • Softphones register fine.
  • can make extn to extn calls OK.
  • Have flushed and disabled iptables :
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X
iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT​
  • Firewall rules work. Tested using Hercules to confirm ports accepting traffic on port 5060 etc.
  • SIP ALG disabled.
  • Whitelisted the ITSP IP address in the "Blacklist IP Addresses"
  • Pro Licence applied.
  • configured with FQDN and SSL, all working perfectly from the outside world.
Havent changed the firewall. Currently there are 25 SPA504G phones registering off site to a hosted PBX which we are migrating from. I am wondering if all those NAT sessions are breaking my inbound SIP rule?

Any suggestions here would be apprecated!
 
Last edited:
Make use of the 3CX Activity Log. Does an inbound call show in the logs? If not, then there may be something (external firewall, port settings, provider configuration), that needs to be changed. If a call does show, then what do the logs show happening to it? That will tell you what needs to change in 3CX.
 
Last edited:
Thanks for the replies. Sadly, the activity log show no attempted inbound calls.
Ive installed a number of 3cx instances now and have spent 12 years in traditional telephony incl SIP / VoIP and networking.

The trunk works. I can point it at another 3CX instance and it works fine.
Yes, I have inbound call routes.
Outbount calls work fine.

Im not convinced its not Debian causing the issue I might install it in my office with the customers configuraton and see what happens.
 
You might try using Wireshark, between the modem and the first device, or, talk to your provider, and see if they can tell you why the call doesn't reach you. Might be a registration setting that is giving them with an incorrect IP/port to contact you on.
 
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