FXS WITH FAX MACHINE ISSUE

[Wilson Baez]

I have FAX machines connected to FXS ports on 2901 routers, MGCP. I think I have all configures right, however I have an intermitent problem, we are getting poorline condition when trying to fax. I'm thinking that it may be a bad trunk on one of the PRI's

I would like to know if there is a way to force the FXS port to pick a especific trunk so i can test one by one to find which is the one cuasing the trouble.

Please if you have any suggestions let me know.

Thanks all

[Chris Deren]

What fax protocol are you using, i.e. T38, passthrough, relay?  Ensure the same is configured end to end.

Can you post "sh controller t1/e1" from the GW where the PRI is connected? You need to ensure there are no slips/errors on the line.

Chris

[Wilson Baez]

I'm using passthrough and have configured the same in both ends. The controllers t1 where the PRI are connected all show

Total Data (last 24 hours)

     0 Line Code Violations, 0 Path Code Violations,

     0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,

     0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

GC2821VGW-1#

Total Data (last 24 hours)

     0 Line Code Violations, 0 Path Code Violations,

     0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,

     0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

GC3845VGW#

Should i try a different fax protocol?

[Chris Deren]

Please post all relevant configuration from each GW in the path, ie. PSTN GW as well as GW the analog device is connected to.

Chris

[Jorge Armijo]

Hi,

Please take a look on this document for the most common fax call flows:

https://supportforums.cisco.com/docs/DOC-25210

HTH

--
Jorge Armijo

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[Steven Griffin]

Wilson,

T.38 fax relay is the preferred method for transporting faxes across any VoIP network or even between PSTN interfaces on the same voice gateway. 

For MGCP controlled FXS ports you need to do two things:

1. In CUCM, enable T.38 on the voice gateway page

2. On the router, add the following commands:

  mgcp package-capability fxr-package

  mgcp default-package fxr-package

  mgcp fax ecm enable

It also doesn't hurt to enable T.38 when you fall into SRST  or use H.323/SIP.  For that add the following command:

voice service voip

   fax protocol t38 version 0 ls-redundancy 0 hs-redundancy 0 fallback pass-through g711ulaw

-Steven

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