No RTP packets

Discussion in '3CX Phone System - General' started by Aussie_Ben, May 24, 2014.

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  1. Aussie_Ben

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    I have a new install of 3CX which is working fine - at most times.
    3CX is installed on a standalone desktop pc, running windows 8
    Installed version is V12.0.35528.640
    Firewall is not active on the pc.

    Internet access is given by a Belkin ADSL router, this router also has firewall disabled.

    Using the firewall checker within 3CX all ports pass the test.

    When a customer calls our phone number, sometimes after the connection is made there is dead air/silent, no audio for the caller in.
    Then if they try again a few moments later it will work fine.

    When the call in has dead air the activity log always shows;
    [MS105000] C:16.1: No RTP packets were received:remoteAddr=xxx.xxx.xxx.xx:19880,extAddr=0.0.0.0:0,localAddr=xx.x.xx.xxx:9028

    i have tried all methods described in previous posts in relation to this, all to no avail.

    I think it has something to do with the above "extAddr=0.0.0.0:0" is always zero's.
    The remoteAddr is my VIOP provider and the localAddr is my static ip from my ISP.

    Hardest thing to identify as sometimes it will work fine all day, then all of the sudden an incoming call will connect to our system but will hear no IVR or audio.

    Any help will be much appreciated.
     
  2. jpillow

    jpillow Well-Known Member

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    Sounds like a firewall issue to me, I've learned because a firewall passes the firewall test doesnt necessarily mean its performing correctly.
     
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  3. lneblett

    lneblett Well-Known Member

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    You will most likely need to get a wireshark capture and then look at the telephony tab and get the flow so you can see how both a successful and an unsuccessful call are seen (or not) by 3CX. You will see the SIP servers communicating and then see the media server come into play which is how the RTP packets are handled (on a successful call). Likely comparing the calls you will see the absence of a media server; hence why no audio. The phone will ring, you will answer and on a bad call, will enjoy dead silence.

    Take a look at the router and ensure that the SIP ALG is off. I had an instance a couple of weeks ago with an Arris cable modem and built-in wireless with router that while the firewall was down, and the SIP ALG was shown to be off, it still intermittently acted as the SIP ALG was on. The frustrating thing was that if you unplugged the device, it would come back and act normally for a while, but then would revert some time later. I finally had to escalate the issue to the cable company's 3rd tier support, who also verified the settings as being correct, but I had the good fortune of getting a tech who understood and agreed to change the modem out. Since then, all has been well. The SIP ALG will normally alter the IP addresses and will send the audio to an invalid IP. I do not know why, in my case, the modem worked sometimes and failed at others, but I could clearly see the issue in the wireshark capture.

    I also agree that the firewall test is an indication and not an absolute. It always passed in my case, but then the ALG never came into play.
     
  4. jpillow

    jpillow Well-Known Member

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    Are these remote extensions or onsite? Als a wireshark capture or server log replicaitng the issue would also be helpful.
     
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  5. Aussie_Ben

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    Thanks jpillow & lneblett.

    I may have failed to mention i am a noob :D

    All my IT colleges also say that it is a firewall issue, but as i mentioned the firewall is turned off on both the PC that is acting as the 3CX phone server and on the ADSL router.

    All the extensions are on site.

    I will will try the wireshark steps and try to identify the no audio inbound calls.

    I will also try to swap the ASDL router to see if it is that.

    It works for a while if i restart all the services within 3CX or if i restart the PC, maybe looking at the router as the cause i suspect.

    Process of elimination i suppose.
     
  6. jpillow

    jpillow Well-Known Member

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    What are youe planning on swapping out the ADSL router with? If it is provided by your ISP I'd forgo that as well, and purchase a that is modem to work well with VoIP. Do you have the Belkin ADSL in bridgemode and the Watchguard acting as firewall/router? Maybe if you tried repliacting the issue take a look at the wireshark, and server logs that would give you more if an indicator of where the issue lies. Post the logs just insert xxx.xxx.xxx.xxx's for ips etc...
     
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  7. Aussie_Ben

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    Funny you should say that.

    The network environment i have here is that the Belkin ADSL router goes straight to a WatchGaurd Xtm25 firewall. Then from the watchguard to the switch.

    I tried plugging the pc that acts as the 3CX phone system straight to the Belkin ADSL router and by-passing the Watchguard to see if it was that, but i still experience the same problems.

    So that rules out the watchguard firewall.

    Thought it may be just the model of the ADSL router that may be causing the probs, so thought of trying another router to see if that improved things.

    The router was not provided by ISP, just store bought.
    Having said that, maybe worth asking them what router they recommend
     
  8. leejor

    leejor Well-Known Member

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    I find that the combination modem/routers, while providing simplicity, are not always the best choice when it comes to something more complicated than "surfing the web". If they are supplied by the provider then they usually give your provider access to your network/settings for troubleshooting (great for the majority), while being sparse on features. Some will also include in-built VoIP features that while they may not be used at present, can cause conflicts with 3CX. For those reasons I avoid them, and given the choice, recommend that to others. Of course it isn't always possible.

    That said, if you have a chance to try a stand-alone modem, and a router, then it gives the chance to bypass the router and eliminate it as the problem.

    If you list the model number of the modem/router (and perhaps the provider you are dealing with), someone else on the forum may have experience with it. It may simply be one setting that needs to be changed.

    There is also the (remote) possibility, that your Belkin is faulty, given, that it works on occasion. On occasion, a complete reset, and re-provision, can help.
     
  9. dagsworth461

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    So what was the resolution?
     
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