SIP VIA Header

Discussion in '3CX Phone System - General' started by dom, Aug 16, 2013.

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  1. dom

    dom

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    Hi,

    I'm a newbie to 3cx, and am struggling to get my phone system to make outbound calls.

    The reason is that the VIA header is being set to my servers local address, not its external IP, this has been confirmed by my VoIP provider with the use of wireshark

    Which setting in 3CX sets this field? I have turned of STUN and specified my servers external IP manually, but it seems to ignore that field.

    Thanks!

    Dom
     

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  2. lneblett

    lneblett Well-Known Member

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    was the system always set to the same settings as that which you show? is your public ip also set to the same as shown but on the public ip tab?

    more importantly, go to the voip provider tab and then edit and then look for advanced where you should see the options.
     
  3. dom

    dom

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    I changed it from STUN to Static IP, but other than that, I haven't changed anything.
    The public IP tab has the exact same IP entered in the field.

    I had a look under the VoIP provider>Advanced options but al of those options are for a VoIP provider who requires registration, mines doesn't.

    My VoIP provider tell me that they are expecting our public IP in the VIA header, and that's why they are rejecting our calls.

    See the attached wireshark scan. The highlighted section has out local IP in the VIA header, not the public.

    very confusing!
     

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  4. bardissi

    bardissi Member

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    Check Settings, Network, Static IP, Static Public IP
     
  5. dom

    dom

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    annoyingly, that is also set to our public IP!
     

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  6. lneblett

    lneblett Well-Known Member

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    Sorry, but to me, the VIA header looks correct given what you have displayed. The VIA is used to indicate "the path or proxy" by which the invite traversed. The connection IN (C) underneath the SDP should be reflecting the public IP that the provider seeks.

    When you initiated the call, the data flowed from the phone to the system and as a result, the initial "VIA" (should of) had the address of your phone. Then the system, communicated with the provider, which the "VIA" should of had the IP of the system, but the connection info should have been the IP as set by the advanced parameters which would be your public IP.

    So, the path the routing took is the VIA and conversely the provider should be providing the same thing in reverse. A proxy can alter the VIA if one is set. The VIA used in conjunction with the other IP related headers or values such that it eliminates the need for any resolution or lookups (other than to the provider in the initial invite) as each step is spelled out implicitly in the flow.

    In response to your other post about the provider not needing registration -
    This may be true, but this does not mean that they may not be looking at the stream and reacting accordingly. I am somewhat surprised about the issue as most providers who do not require registrations require a fixed IP at sign-up or activation and that IP is already a part of their database. If they can match, then all is good. I use a provider who does not require registration, but I use it anyway as it helps to know whether the trunk is there or not proactively - shows green or red. I had suggested using it so that regardless of their need, it would just reinforce the path you needed. I use "specify" and insert the public IP. Again, because they may not require it does not mean that they don't support its use.

    Perhaps your provider does indeed need something different which is when I suggested the need to look at other optional settings, but only after eliminating those that would normally be used. I still suggest changing the VoIP provider registration as suggested and trying as there is nothing to lose.

    Can you at least share who the Provider is? Others may be using and can better advise?
     
  7. dom

    dom

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    Thanks, that was exceptionally helpful and informative.

    All you said there makes sense to me, This 3CX server PC is behind a Draytek router, so I presume I need to configure the Draytek to add an extra VIA header to describe its position in the SIP chain? or am I missing the point?

    I'm using a Gamma SIP trunk

    I will have a play around with the registration settings tomorrow, when I get back to the office.

    Thanks again.
     
  8. lneblett

    lneblett Well-Known Member

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    Take a look at this -

    http: //www.3cx.com/blog/voip-howto/gamma-voip-provider-trunk/- NO LONGER AVAILABLE
     
  9. benratty

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    Anyone know what happened to this link or any instructions for setting up Gamma on v14 so I can check
    http: //www.3cx.com/blog/voip-howto/gamma-voip-provider-trunk/ NO LONGER AVAILABLE

    Cannot find any setup instructions at all for Gamma on 3cx and above link is dead now
     
  10. NickD_3CX

    NickD_3CX Support Team
    Staff Member 3CX Support

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