Proxy Mgr odd behaviour

Discussion in '3CX Phone System - General' started by amos.max, Oct 7, 2011.

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  1. amos.max

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    Hi All,
    I'm trying to set up a remote phone via the SIP Proxy Mgr. The SPM tunnel seems to be established ok, but can't get the phone to register (408 - timeout).
    3CX softphone works in tunnel mode form the location, but not via the SPM.

    I can see the registration attempt in the SPM Logviewer and in the server tunnel logs as well:

    Code:
    .\Bridge.cpp(418) : [13:22:33.635](Trace5):Got SIP msg
        brief=SipReq:  REGISTER internalPBXIP tid=937904223 cseq=REGISTER contact=105@remotePhoneIP:5060 / 2000 from(tu)
        from tunnel's connection remoteLocIP:2193
    .\Bridge.cpp(433) : [13:22:33.635](Trace5):Selected SIP stack on internalPBXIP:5080
    .\Bridge.cpp(715) : [13:22:33.635](Trace5):Process tunnel request: REGISTER
    .\Stack.cpp(162) : [13:22:33.635](Trace5):Sending to stack(5080);
      brief=SipReq:  REGISTER internalPBXIP  tid=937904223 cseq=REGISTER contact=105@remotePhoneIP:5060 / 2000 from(tu)
    .\Stack.cpp(102) : [13:23:05.650](Trace5):Received from local SIP stack(5080):
      brief=SipResp: 408 tid=937904223 cseq=REGISTER / 2000 from(wire)
    .\Bridge.cpp(304) : [13:23:05.650](Trace5):Processing SIP message (tid=937904223) from SIP stack internalPBXIP:5080
    .\Bridge.cpp(662) : [13:23:05.650](Trace5):Process local response: 408 Request Timeout / REGISTER
    .\Bridge.cpp(365) : [13:23:05.650](Trace5):Tunnel to remoteLocIP:2193 is selected for SIP message (tid=937904223)
    This is where it gets odd: I suspected our office firewall blocking something, so I did a trace. It seems the PBX is attempting to send UDP:5080 packets to the IP address of the computer where the SPM is installed. This is in fact blocked on our firewall, but even if it wasn't, that IP is not routable (private class C).

    It seems to me that the PBX is not using the tunnel to respond to the registration request (I can see those outbound attempts every time I try to register an extension via the SPM).

    I'm sure it's some simple configuration mistake on my part, but I can't seem to figure it out.
    Any help and/or pointers would be greatly appreciated!!
    Thx&Rgds - Marcus.
     
  2. SY

    SY Well-Known Member
    3CX Support

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    Stop hovering to collapse... Click to collapse... Hover to expand... Click to expand...
  3. amos.max

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    Hi Stepan,
    thx for your reply and my apologies - I should have been a little bit more clear.
    The connection attempt in the log excerpt I posted is from a Grandstream 2110. I just used the 3CXPhone to verify the tunnel is set up correctly on the server side.

    I had already looked at the links you posted, unfortunately there are no specifics regarding network configuration at the remote site. Are there any ports at the remote site that need to be opened for the SPM to function properly?

    I'm also still wondereing about those packets the pbx is trying to send back to the SPM (the destination is the PC running SPM - not the phone).

    Thx again.
    Marcus.

    PS: will do (code listings) :)
     
  4. leejor

    leejor Well-Known Member

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    3CX and the proxy server use ports 5090 and 5080 to communicate (one each direction in the Tunnel). These can be changed in the settings at both ends if there is another port that is more suitable. Otherwise you should be forwarding port 5080 in the router at the remote end, to the IP of the Proxy Server.
     
  5. amos.max

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    Thx for the comment, but as I mentioned above the target address the pbx is trying to send those packets to is a private class C address (e.g. 192.168.x.y) -> non-routable on the Internet, so even if I did open up stuff on either end those packets would not reach their destination.

    Again, the 3CX softphone works flawlessly from a pc on the remote network. A hardphone via the SPM does not. Is there something fundamentally different in the functionality or connection of the softphone using the tunnel and the SPM? In other words, can I deduce from the fact that the softphone works fine that everything is set up as it should be (server side)?

    Thx again!
    Marcus.
     
  6. leejor

    leejor Well-Known Member

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    If 3CX is trying to send back to a private IP, then I would think that it has something to do with STUN settings in the SPM. It must be registering, with 3CX, using the private address rather than the public one, of the router, that it is behind.
     
  7. amos.max

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    That sounds promising, but there doesn't seem to be any way of configuring STUN settings in the SPM ... (??)
    I did also a wireshark capture thins morning and I can see those sip request packets going to that private address. Interestingly enough, the packet contains all the tunnel information (remote tunnel NAT and internal IP). I also can see other packets that are clearly using the tunnel connection (some weird port - 4847).

    @3CX Support (Stepan): is it possible to purchase a single support incident? Or is all support delegated to partners?

    Thx&Rgds,
    Marcus.
     
  8. amos.max

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    For all those that may be interested, this is the solution:
    The GrandStream GXP2110 has an option called "Remove OBP from route" that needs to be set to "Yes".
    I do not know if this setting also exists on other models.

    According to GrandStream support this option "is for the SIP Extension to notify the SIP server that it is behind a NAT/firewall. When using outbound proxy field the phone would add a route header, which might not be handled well when using with 3cx PhoneSystem tunnel."

    Now I just need to fix the voice quality issues ...

    Thx&Rgds,
    Marcus.
     
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