Author Topic: External Transfer on 3300 with SIP  (Read 1782 times)

Offline WGAIT

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External Transfer on 3300 with SIP
« on: October 11, 2016, 11:24:34 AM »
Hi all,

We have a Mitel 3300 using a SIP supplied by a national UK provider. 

Everything works as it should, but we're unable to transfer calls to an external number.  For example, if someone calls our office, and we want to transfer that call to a staff member's home number (if they're working from home) the call goes through but there is no voice, on either end.

We used to have a SIP trunk provided by BT, who used a Proxy, and this external transfer worked fine.  We've made no other changes other than the SIP provider (who don't use a Proxy).  We're assuming it's Firewall/NAT related, but Wireshark shows both RTP streams are successful, and there's no lost packets, it's almost as though the two streams aren't being connected together as a complete call.

Wireshark shows the internal IP address of the Mitel handset making the external transfer on the OK200, which I gather is normal for a Mitel system, should this be set to the external IP address of the PBX somehow, or is this behaviour OK?

Does anyone have any ideas?  Thanks
« Last Edit: October 11, 2016, 11:29:20 AM by WGAIT »


Offline dilkie

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Re: External Transfer on 3300 with SIP
« Reply #1 on: October 11, 2016, 12:13:49 PM »
are you using an MBG between the 3300 and the sip provider to provide trunking?

Offline WGAIT

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Re: External Transfer on 3300 with SIP
« Reply #2 on: October 11, 2016, 04:57:25 PM »
Hi, thanks for the reply, there is no MBG.

Offline ralph

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Re: External Transfer on 3300 with SIP
« Reply #3 on: October 11, 2016, 05:06:02 PM »
If your MBG is in the DMZ or another VLAN other than your voice VLAN then I'd venture to guess that the carrier's router doesn't have a route to it.
Have the carrier test by pinging the MBG from the router.

Ralph

Offline dilkie

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Re: External Transfer on 3300 with SIP
« Reply #4 on: October 11, 2016, 05:21:25 PM »
Hi, thanks for the reply, there is no MBG.

Without an SBC of some sort, it's not going to work... that's what the MBG does for you, provides SBC functionality to anchor the signalling and media so NAT traversal to your carrier works correctly.

Offline WGAIT

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Re: External Transfer on 3300 with SIP
« Reply #5 on: October 12, 2016, 05:13:13 AM »
Thanks all for your assistance.

Offline Dogbreath

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Re: External Transfer on 3300 with SIP
« Reply #6 on: January 24, 2017, 08:50:11 AM »
"SBC of some sort" is not limited to MBG of course. Pretty much anything Asterisk or Freeswitch-based can do this. You then gain CDR logs, real time SIP debugging, ability to block nuisance numbers and sundry other things that you wish existed in MCD but don't.


 

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