SRST Fallback - no ephone-dn assigned to extensions

We have installed CCM 7.1(3) with a H323 Gateway, running IOS 15.0(1)XA,. We are in the process of testing SRST with this gateway, but it doesn´t appear to work fine. When in Fallback mode, the phones show the "Fallback mode" on screen, but get no extension. We have tried several IOS 12.4T versions, but the problem stays the same. Also according to the compatibilit matrix with CUCM, we need to run at least SRST 7.2 or 8.0 to support CUCM 7.1(3). Any ideas why the ephones show available_line=0?

SRST8.0: 7937 with sccp version 17 would not register to SRST.

Symptom

IP phones running firmware that uses sccp version 17 can not register to SRST/CME-SRST or will register but not obtain any lines.

Conditions

SRST router running 15.0(1)XA. This is the first image with sccp version 17 support for SRST.

Workaround

Download the IP phone firmware to a version that does not use sccp version 17.

For 79x1/5/2 phones and 7970s this is 8.4 firmware.

For 7937 phones get a load prior to 1.4(1).

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Please click here for a list of Cisco Unified SRST 7.1 Supported Firmware, Platforms, Memory, and Voice Products

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