cisco 3945 router

[Syed Akbar Ali]

Dear Support Community ,

previously we have cmm model on core now we are upgrede the E1 on Cisco 3945 router .

under "voice service voip" on cmm model its configure as  " fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco"

but on 3945 router its taken as " fax protocol t38 version 0 ls-redundancy 0 hs-redundancy 0 fallback none"  little change from cisco to none  does its work fine  shall i need to configure as  "

fax protocol t38 version 0 ls-redundancy 0 hs-redundancy 0 fallback pass-through g711alaw .

and even in the dial

on CMM model

dial-peer voice 54 voip

destination-pattern xxxx

voice-class h323 1

session protocol sipv2

session target ipv4:x.x.x.x

dtmf-relay rtp-nte

codec g711ulaw

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

no vad

!

on router 3945

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback pass-through g711alaw.

so please advice which one we need to configure for the fax services  none or pass-through g711alaw because cmm we use as cisco now its not available .

highly appricated for your fast response.

Thanks

Syed

or

[paolo bevilacqua · Accepted solution]

It doesn't really make much difference, because in a normal setup, there is never fallback.

[Jonathan Schulenberg]

Just adding root cause: The PVDM3 modules in the ISR G2 hardware no longer support proprietary [legacy] Cisco Fax Relay. They only support fax passthrough or T.38 fax relay.

As Paolo stated, assuming everything is behaving and supports T.38 (more on that in a moment) you should be fine since they will negotiate T.38. If something doesn't cooperate they will not have compatible fallback options and the fax would fail at that point. The most common example of a device that supports ONLY passthrough is the ATA-186. It didn't have the CPU capacity to run relay, cisco or T.38.

Since the older CMM and 3800 hardware also supports g711ulaw fax passthrough I suggest updating the config on the legacy hardware to do that for fallback instead of cisco fax relay.

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