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New Member


Does SRST support fallback so that calls can go out of a PRI? Any links to documentation?

New Member

Re: SRST and PRI

If I understand your question correctly, Can you have calls go out a voice PRI when in fallback. Yes, I have a "dial peer voice pots" configured with a destination pattern of 9T pointed at the voice pri port. In the event your data pri goes down, all calls will be routed over the voice pri. Is this what you were looking for?

New Member

Re: SRST and PRI

Survivable Remote Site Telephony (SRST) is a Cisco router IOS feature set that uses the Skinny protocol to provide call-handling support for the local IP phones if the WAN connection to a central site Call Manager fails. During a failure, if this feature is enabled, the Cisco IP phone displays a message to indicate that it is in Cisco SRST mode and its functionality is limited, mostly to just calling on the remote site network. The SRST feature also provides centralized call processing with telephony service backup including off-net calls to 911. The Cisco IP Phone 7960/7940 displays the message "CM Fallback Service Operating." The Cisco IP Phone 7910 displays the message "CM Fallback Service."

When the Cisco Call Manager is restored, the displayed message is removed and the full functionality of the Cisco IP phone is restored.

Depending on the configuration, the following features can be maintained in fallback mode:

(1) Re-homing of IP phones to a local router

(2) Local Extension-to-Extension calls

(3) Extension-to-PSTN calls

(4) Existing calls upon recovery

(5) Support for IP and POTs phones

(6) Speed dial and last-number redial

(7) Direct Outward Dial Calling (DOD) calling

(8) Direct Inward Dial Calling (DID) calling

(9) Caller ID and ANI support

etc. etc.

Hope this helps.

F C Wood

Houston, TX

Cisco Employee

Re: SRST and PRI

Support for PRI on SRST fallback mode is limited to 5ess, Net 5 and NI2 protocols for 12.1(5)YD5.

Take a look at:


New Member

Re: SRST and PRI

Any ideas when SRST will be available on 12.2?

Thanks for the info.

New Member

Re: SRST and PRI

12.2(2)xb2 supports SRST.

Cisco Employee

Re: SRST and PRI

12.2(2)XT1 has SRST version 2.

New Member

Re: SRST and PRI

I am using the new 12.2(2)XT1 code on a 3640. With Call manager 3.13a In fallback more the phones (7960/40) do not register "registration rejected" does anyone have this combination working??