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New Member

Will IOS 15.X Support Cisco FAX Relay?

Dear All,

     Will Cisco 2911 running 15.x support cisco fax relay?

I cannot find out this command, it seems it only support T38 and fax passthrough.

My customer have many VG248 and theVG200 voice gateways are running cisco fax relay, FAX works fine.

We need replace the old voice gateway with Cisco 2911 (IOS 15.x), no fax relay command is found.

It indicate fax passthrough works with VG248 (running SCCP). 

Vg248 is support T38 NSE mode, cisco relay and passthrough mode, it indicate only fax pass through works with new 2911.

End user afraid that new 2911 CANNOT work with existing VG248 that is configured with cisco fax relay and want us to define

cisco fax relay on Cisco 2911 but no such command in 15.X ios.

Can anyone have information or solution regarding this case??




Will IOS 15.X Support Cisco FAX Relay?


Line from below link

Q. Do the PVDM3 modules have feature parity with PVDM2s?

A. Yes, all features supported by PVDM2s are supported on PVDM3s, with the  exception of Cisco Fax Relay and G.723. Cisco Fax Relay and G.723 are  no longer supported on PVDM3s. Customer can still use PVDM2 to obtain  G.723 codec support or use G.729 codec on PVDM3 as alternatives.

And PVDM goes in ISR G2. SO SIR G2 do not support FAX Relay.


Ronak Patel

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New Member

Re: Will IOS 15.X Support Cisco FAX Relay?

Dear Sir,

Many thanks for your reply!! It help me to understand the root issue!



Hall of Fame Super Gold

Will IOS 15.X Support Cisco FAX Relay?

Cisco Fax Relay is the legacy, obsolete transport method.

Since VG248 supports T.38, that is the standard that you will use to have it work with ISR G2.

New Member

Will IOS 15.X Support Cisco FAX Relay?


Yes, I had defined t38 on 2911 using h323 or MGCP (NSE or protocol base)  and t38 on VG248, but it did not work. It fallback to passthrough mode.Refer the following Q&A regarding FAX,  VG248 is using NSE-based T38.

My customer have 10 sets of VG248, it involve too many FAX devices.

User want to use existing VG248 until end of support from Cisco and will not replace 248 with VG224.

Q. Can you use a SCCP gateway (VG248) with MGCP PSTN gateway and use both methods (Standards-based T38 and NSE-based T38) at same time?

A. No, both switch over methods are not possible at the same time for T.38. On the VG248, only one option is possible.

Q. Will SCCP protocol ever support standards-based T38?

A. No plans at this time.


Hall of Fame Super Gold

Re: Will IOS 15.X Support Cisco FAX Relay?

Not good, but if you can have things be within a supported configuration (T.38), and they don't work, you can contact Cisco TAC for a solution.

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