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14400 fax speed limit using modem passthrough on VG204XM and 2921 voice router

Hello,

I am attempting to achieve faster faxing, while also allowing credit card machines (modem based) to work using the same equipment and configuration. Fax passthrough, T.38, etc seems to break the credit card machines. Modem passthrough works for both. But by "works" I mean that I can never achieve a better speed than 14.4k on the faxes. Perhaps this is to be expected? I was reading that if I am using modem passthrough, an the bandwidth is there (it is), I should be able to see double that.

Is anyone using the analog equipment and getting so called "high speed" faxing?

Some config snippets ...

On my VG204XM, running vg20xxm-advipservicesk9-mz.155-1.T2.bin

voice service voip
 fax protocol none
 modem passthrough nse codec g711ulaw

On my 2921, running c2900-universalk9-mz.SPA.152-4.M6a.bin

voice service voip
 fax protocol none
mgcp modem passthrough voip mode nse

My equipment is attached to the VG204XM, which is being managed by CUCM 8.6.2. Not sure if any of that matters, since this device seems to ignore most of the call manager settings. I am attaching a snapshot of those settings anyway. The 2921 has a T1 line out to the telco (so it's a short trip for this traffic). I have all 1G connections in-between.

I am also attaching a sample of the debug output.

Thanks in advance for any advice!

 

1 Reply 1

Gordon Ross
Level 9
Level 9

14.4 is the best you'll receive on a VoIP system without going to modem or fax-relay technologies.

 

GTG

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