[cisco-voip] Fwd: Cisco ATA Fax Confusion

[Ryan Ratliff]

I ran this by somebody that actually works fax issues every day and there are two ways your call can be working.

The first is that modem passthrough is actually being used.  This can be confirmed by waiting 10 seconds after the call is answered and looking at the output of 'show call active voice brief'.  If you see modem-pass here then it's switched to modem passthrough.

The other option is that it has fallen back to g.711 low speed fax and you are getting lucky. 

-Ryan

On Jan 22, 2010, at 4:15 PM, Ryan Ratliff wrote:

Are your calls working in one direction only or both ways?  We are all in agreement that the ATA only supports NSE based passthrough and I do know that the default fax protocol on cisco routers is modem passthrough so maybe there's another bit of your config that's allowing the call to proceed.

In the doc you referenced it mentions that no fall-back will still allow for the fax to proceed if modem passthrough is configured.  Maybe this also applies if fax pass-through fallback isn't successful. 

-Ryan

On Jan 22, 2010, at 3:50 PM, Rhodium wrote:

Yep, I am aware of the hyphenations. Been trying to use them in the right context if you look at my emails. ;o)

I don't think the fall back command applies to NSE passthrough but protocol based pass-through:

http://www.cisco.biz/en/US/docs/ios/12_3/vvf_c/cisco_ios_fax_services_over_ip_application_guide/t38.html#wp1156682

Also, the written documentation I have shows it under protocol based pass-through.

Which led me to ask the question, why is it working? Are you sure that it refers to protocol based pass-through and not NSE?

Regards,

Jason





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