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Fallback behavior on the SPA8800


I have a SPA8800 connected to two PSTN lines and two analog phones and all of them register as trunks and extensions on a asterisk server, where many other IP phones also register. The SPA works as a gateway between the internal VoIP phones and the PSTN.

Last year, there was a power failure and we still could make and receive calls to and from the PSTN. The idea of the two analog phones was to provide communications when out of VoIP. That is desirable.

However, when the sip proxy is unreachable (on the same LAN, but out of service), I noticed that I can make calls from the analog phones to the PSTN (Auto PSTN fallback set to YES). But, on the same circumstance, incoming calls do not ring on the analog phones.

How can I configure the box in order to make incoming PSTN calls answered by the associated analog phone when the sip proxy is unavailable?

Thanks. Regards,



Eric Moyers
Rising star
Rising star

Hi, My name is Eric Moyers. I am a Network Support Engineer in the Cisco Small Business Support Center.

It was brought to my attention that your post had not been answered yet, so I wanted to let you know I am going to research this for you and get back to you with an answer. I apologize tht no one has responded to you before now, but I will get you an answer to your question shortly.

Eric Moyers
Cisco Network Support Engineer



Based on my understanding of the way this the gateway works, only outbound calls can be directed to the FXO trunk when registration fails to the PBX/SIP trunk.

Per the administration guide, Page 98:

When Line 1 VoIP service is down (because of registration failure or loss of
network link), the ATA device can be configured to automatically route all outbound
calls to the internal gateway using the parameter listed below.

From my understanding, if you have a traditional PBX system in place, an inbound call is going to need a SIP UA (User Agent) to direct the call and set up the SIP messaging to begin that call. Hence, without a reachable local PBX, your inbound calls are incapable of coming in.

This would be expected behavior for this device.



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