Outbound DTMF issue with Aastra phones

Outbound DTMF issue

I am having a problem with DTMF working reliably outbound on a trixbox v2.6.0.0 using Aastra SIP phones. This is a fresh Trixbox installatrion.

We have 6 Aastra 480i and 4 Aastra 480i CT phones. The RTP settings on all phones are:
RTP Port - 3000
Basic Codecs - unchecked
Force RFC2833 Out-ofBand DTMF - unchecked
Customized Codec Preference List - (empty)
DTMF method - RTP
Silence Suppression - unchecked

The Extensions are all set to dtmfmode=RFC2833 in freepbx

The trunk is vitelity. The SIP PEER info is:

context=from-trunk ; (this could be ext-did or from-pstn as well)

There is no firewall issue. The trixbox is on a COVAD T1 with a static, public IP.

On the 480i’s. if I set the RTP settings to RFC, voicemail and other system features that require DTMF are accessible, but outbound DTMF is still unreliable. Same issue with setting RTP on the Aastra’s to “Both”, except that the DTMF problems appear on different called numbers (for instance, Walgreens IVR now works but BofA doesn’t). If I set the RTP settings to SIP Info, outbound DTMF works reliably, but then I cannot access trixbox voicemail.

I do not have this problem with Grandstream phones with DTMF set to “in-audio” and RFC2833."

Any idea how to fix this problem? If I can’t fix it, I’m going to have to send all of the Aastra phones back and exchange for Gransdtreams or Cisco’s.

I’d contact Aastra support directly as something does not sound right. It could be a setting in the Phones UI or even in the web UI overriding settings in the config files.