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RightFax and T38


We have several voice gateways in our network (MGCP) that are set with "mgcp fax t38 inhibit". Without this syntax, I've always had problems with regular fax devices on a Cisco VoIP network. In the normal course of things, this is not an issue. However, recently we've implemented RightFax which requires that T38 be allowed. Now, in order for RightFax endpoints to fax regular fax machines, they have to 10-digit dial through a specific gateway that has its own PRIs and DID ranges. 5 digit RightFax-to-CiscoFax and vice versa does not work. Has anyone else seen or dealt with this issue?



Re: RightFax and T38

I realize this is an older post, but I am in a similar situation and am interested in others experience with Callmanager/RightFax integrations.

I've specifically turned off mgcp t.38 on all voice gateways as this caused problems with faxing (usually from old fax machines). Our current plan is to use the callmanagers for all call control to the RightFax servers (inbound and outbound) and I would be interested in hearing others experience with this setup.


UCCM: 7.1.3

RightFax: 9.4 (I think)

MGCP controlled PRI gateways (2821's & 3845's): IOS 12.4(24T2)

Community Member

Re: RightFax and T38

Hey Brad,

     Wow, this was a while ago and I've worked through the issues, so hopefully I can be of some help.  I found in our RightFax implementation that if you have a single voice gateway that you need to be able to support RightFax and old fax machines, use H323.  When you deploy RightFax you will need to configure settings (like ECM) which are troublemakers for old fax machine.  You will have more flexibility if you use H323.  I can't remember the details, but if you use MGCP, the RightFax-specific settings will cause problems and you will be directed to use H323 instead.

     Fortunately, I had an extra 2811 lying around, so I provisioned a separate PRI and voice gateway just for RightFax (and use MGCP).  I like this approach a lot better since it allows me to segment off the RightFax transmissions and can make changes to that gateway without worrying about breaking the production voice gateway that's used for everything else.

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