Voxtelesys trunks going down

[Richard10]

Several of my customers using 3CX hosted are having their Voxtelesys trunks go down with a network or DNS error. Service restores relatively quickly but it's been happening repeatedly all weekend and today. Anyone else running into this?

 

[CB2021]

Hi Richard,

Do you have a ticket open with support or sales in regards to these trunks going down?

 

[Richard10]

We opened a ticket with Voxtelesys, which is at the "did you reboot the PBX stage"...

 

[YiannisH_3CX]

Hello Richard,

What is the exact error you are getting? Are all customers on Hosted by 3CX? Are you only having this issue with Voxtelesys trunks or do you other trunks having this issue? Any other issues that might point to a network issue? Choppy audio, SBC's disconnecting?

 

[Richard10]

Hi, the 1st message is usually:
"Trunk L:10000(Voxtelesys) has changed status to unregistered"

Followed by:
"Registration at Voxtelesys has failed.

Destination (sip:3cx.pstn.voxtelesys.net:5061;transport=TLS;lr;maddr=23.155.18.54) is not reachable, DNS error resolving FQDN, or service is not available."

Followed by:
"Trunk L:10000(Voxtelesys) has changed status to registered"

I have 1 customer that has both Voxtelesys and Callcentric. I don't get anything about the callcentric trunk going down, but it doesn't necessarily work the same.

These just came in on a customer who I rebooted last night.

 

[Kevin@voxtelesys]

Hi Richard,
Our latest update was to try disabling TLS on the trunks to monitor via UDP.

 

[YiannisH_3CX]

@Richard10 Since Voxtelesys is looking into this you are in good hands. We will take over if it turns out to be something from our end.
@kevin please let us know if you need assistance with the investigation.

 

[Richard10]

Not wanting to just "change everything" on what has otherwise worked for several months I have been waiting to see if things stabilize. I have not moved away from TLS (don't want to as I have some non 3cx customers that pretty much need it). I have not gotten a failure in 24 hours. Not sure the source of problem.

 

[Mr. Sea]

Curious, we are seeing the same issue occur randomly. I've actually dug through the logs and keep seeing this happen in the same window we get the Error 12293:

3CXMediaServer[1435201]: assertion failed: /Sources/3rdParty/resiprocate/resip/stack/TransactionState.cxx:781: !sip || !(state->isFromTU(sip) && sip->isRequest() && method == ACK)

I also have a ticket in with Voxtelesys, but this looks like a 3CX issue if you ask me.

 

[Kevin@voxtelesys]

Curious, we are seeing the same issue occur randomly. I've actually dug through the logs and keep seeing this happen in the same window we get the Error 12293:

3CXMediaServer[1435201]: assertion failed: /Sources/3rdParty/resiprocate/resip/stack/TransactionState.cxx:781: !sip || !(state->isFromTU(sip) && sip->isRequest() && method == ACK)

I also have a ticket in with Voxtelesys, but this looks like a 3CX issue if you ask me.

Can you DM me your ticket number? Are you using TLS or UDP transport? What version of 3CX?

 

[Mr. Sea]

Sent DM - For public information, it's TLS and v20U8, although we saw this on v20U7 as well. Seems like something with TLS and ACK failure from what I can gather - I've since turned logging to verbose in hopes we can grab more. Packet capture would be great but near impossible since we can't directly reproduce the issue.

 

[Richard10]

It wasn't unique to 3CX. It was all connections that were TCP/TLS, I had to switch everyone to UDP, which in effect negates SRTP as the SRTP keys are negotiated in the SIP messages as I understand it.

 

[egarciapf]

Hello @Richard10

Were you able to figure this out? We are having the same issue BUT seems to happen only when TLS is enabled.

Registration at SIP-TRUNK-VOXTELESYS has failed. Destination (sip:3cx.pstn.voxtelesys.net:5061;transport=TLS;lr;maddr=216.52.108.54) is not reachable, DNS error resolving FQDN, or service is not available. If I run the SIP Trunk check I get this Registrar '3cx.pstn.voxtelesys.net' has a DNS NAPTR record resolving to: _sip._udp.3cx.pstn.voxtelesys.net o=10 _sip._tcp.3cx.pstn.voxtelesys.net o=20 _sips._tcp.3cx.pstn.voxtelesys.net o=30 Registrar '3cx.pstn.voxtelesys.net' has a DNS SRV record '_sips._tcp.3cx.pstn.voxtelesys.net' resolving to: 3cx.pstn.pit02.voxtelesys.net:5061 p=10 3cx.pstn.dfw02.voxtelesys.net:5061 p=10 Registrar '3cx.pstn.voxtelesys.net' has a DNS HOST record (3cx.pstn.pit02.voxtelesys.net) resolving to: [216.52.108.54] Registrar '3cx.pstn.voxtelesys.net' has a DNS HOST record (3cx.pstn.dfw02.voxtelesys.net) resolving to: [23.155.18.54] IP Mode: IPv4 Selected server address: 216.52.108.54:5061 Selected transport type: TLS Selected server domain: 3cx.pstn.pit02.voxtelesys.net Detected Issues The SIP Registration attempt got a failure response [forced unregister] at 05/29/2026 11:47:01 -04:00 It seems like Voxtelesys rejects the registration.

 

[CB2021]

Hello @Richard10

Were you able to figure this out? We are having the same issue BUT seems to happen only when TLS is enabled.

Registration at SIP-TRUNK-VOXTELESYS has failed. Destination (sip:3cx.pstn.voxtelesys.net:5061;transport=TLS;lr;maddr=216.52.108.54) is not reachable, DNS error resolving FQDN, or service is not available. If I run the SIP Trunk check I get this Registrar '3cx.pstn.voxtelesys.net' has a DNS NAPTR record resolving to: _sip._udp.3cx.pstn.voxtelesys.net o=10 _sip._tcp.3cx.pstn.voxtelesys.net o=20 _sips._tcp.3cx.pstn.voxtelesys.net o=30 Registrar '3cx.pstn.voxtelesys.net' has a DNS SRV record '_sips._tcp.3cx.pstn.voxtelesys.net' resolving to: 3cx.pstn.pit02.voxtelesys.net:5061 p=10 3cx.pstn.dfw02.voxtelesys.net:5061 p=10 Registrar '3cx.pstn.voxtelesys.net' has a DNS HOST record (3cx.pstn.pit02.voxtelesys.net) resolving to: [216.52.108.54] Registrar '3cx.pstn.voxtelesys.net' has a DNS HOST record (3cx.pstn.dfw02.voxtelesys.net) resolving to: [23.155.18.54] IP Mode: IPv4 Selected server address: 216.52.108.54:5061 Selected transport type: TLS Selected server domain: 3cx.pstn.pit02.voxtelesys.net Detected Issues The SIP Registration attempt got a failure response [forced unregister] at 05/29/2026 11:47:01 -04:00 It seems like Voxtelesys rejects the registration.

Hello egarciapf,

Can you DM me your ticket number. I can provide this information to our team if you haven't already so we can help resolve this issue.

 

[Richard10]

It sounds like you have a different problem actually. We have switched some people back to using TLS or TCP and they have not had the issue since. It's been about about 6-8 weeks. Honestly if TLS is the only thing not working, I'd be suspicious that you have a certificate problem. (Assuming TCP works fine)

 

[egarciapf]

Thanks, I will do some tests tomorrow. I'll post the outcome.