# Outbound DTMF issue

**URL:** <https://community.asterisk.org/t/outbound-dtmf-issue/22261>\
**Category:** Asterisk Support\
**Created:** [July 30, 2008, 6:56pm UTC](https://community.asterisk.org/t/outbound-dtmf-issue/22261 "2008-07-30T18:56:45Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![chuckjuhl](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@chuckjuhl](https://community.asterisk.org/u/chuckjuhl)\
**Post date:** [July 30, 2008, 6:56pm UTC](https://community.asterisk.org/t/outbound-dtmf-issue/22261/1 "2008-07-30T18:56:45Z")

</div>

I am having a problem with DTMF working reliably outbound using Aastra SIP phones.

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:

type=friend  
username=\*\*\*\*\*\*\*  
secret=\*\*\*\*\*\*\*\*\*  
fromuser=\*\*\*\*\*\*\*\*  
trustrpid=yes  
sendrpid=yes  
context=from-trunk ; (this could be ext-did or from-pstn as well)  
canreinvite=no  
[host=outbound1.vitelity.net](http://host=outbound1.vitelity.net)  
disallow=all  
allow=ulaw&gsm  
DTMF=inband

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.

---

<div class="post-metadata">

**Author:** ![BruceAtMaxup](https://avatars.discourse-cdn.com/v4/letter/b/ecb155/32.png) [@BruceAtMaxup](https://community.asterisk.org/u/BruceAtMaxup)\
**Post date:** [July 30, 2008, 10:38pm UTC](https://community.asterisk.org/t/outbound-dtmf-issue/22261/2 "2008-07-30T22:38:20Z")

</div>

Try dtmfmode=auto in your sip.conf file for those phones. ULAW can handle inband but I’m not sure about GSM.