Take a look at the SRSV feature with Unity Connection.

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/connection/10x/design/guide/10xcucdgx/10xcucdg085.html

That is probably a better fit than independent CUC instances running all over the place.

Does SRSV feature give you the Auto attendant functionality when the WAN is down? From my reading i am only seeing the voicemail feature.

Connection SRSV is used in the centralized Cisco Unified Communications Manager and Cisco Unity Connection environment with multiple branch offices or small sites. It provides limited voicemail and auto-attendant features that remain in synchronization with the central Unity Connection voicemail service so that when the WAN outage or failure occurs, the Unity Connection SRSV solution can provide voicemail service to the subscribers at the branch. However, as soon as the network is restored, all the voicemails received by the branch subscribers are automatically uploaded to the central Unity Connection voicemail server.

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/connection/9x/design/guide/9xcucdgx/9xcucdg085.html

Sorry for the late response guys but thanks for advice. Quick question though, when SRSV kicks in along with SRST, how do incoming calls from the PSTN get forwarded to an AA?

The dial-peers on SRST has to route the call to it.

Hi,

Thanks for the response, are all UCS blade module supported for use with SRSV? The customer has a UCS-E140S module on a cisco 4331 router.

Yes though you have to create the Call Handler locally on that SRSV instance of CUC. Only the mailboxes get synchronized down from the mothership. Take a look at the Complete Reference Guide for Cisco Unity Connection Survivable Remote Site Voicemail (SRSV). There was also an overview and demo of SRSV in the Cisco Live session BRKCOL-2444 - Cisco Unity Connection 9.X Update and New Feature Demos (2013 Orlando). The session recording video covers SRSV around 1hr, 33min in.

Thanks for the information guys, my concern now is that it is 31 sites but based on the documentation it supports 10 per CUC node. Which only allows 20 sites to be supported.

My other option is to go standalone CUC for Auto-attendant option only for each branch site and leave voicemail and call processing centralised. But other than the complex management issue, I am wondering how this can be configured? 

Can you provide some guidance. When someone calls the lines, call manager will connect the call and see that it needs to be answered by the local CUC at the branch site. How will this work?

That's incorrect. Both CUC 10.x and 11.x design guides state "Each Unity Connection SRSV branch supports 500 users per branch with a maximum of 35 branches per centralized Unity Connection server."

If all you want to replicate in the event of a WAN failure is the auto-attendant and you don't care about voicemail then you could use the BACD TCL scripts included in IOS. If you want mailbox access while the WAN is down then you either need to use SRSV with a centralized CUC; or, local instances of CUC at each site that are digitally networked together. The problem with digital networking is that sizing to that scale isn't possible as it maxes out at 10 locations across two Sites or a total of 20 instances of CUC. The third option would be to order RDNIS service on your PSTN trunks and have SRST forward calls to VM back across the PSTN. That's pretty rare though these days.

+5 Jonathan.

The restriction of 20 locations (10 per site with two sites) is applicable for digital networking not for SRSV.

If you are concerned about local AA only not voicemail, another option is to use CUE with IVR license for local sites. This will be running on ISR routers. It will give you more flexibility compared to BACD as you write your own IVR scripts.

Then you can use centralized CUC hosted with CUCM clusters. The drawback that with WAN outage you will lose voicemail facility.

I wouldn't buy CUE at this point. It's on life support, especially in light of CUC supporting the UCS-Express blades. That is my personal opinion only and not a positioning statement from Cisco.

If I understand the question correctly this can be done by CSS/PTs. You can have AA number which resides in site PT and seen by site CSS. This should point to local Branch CUC using HuntPilot or SIP Trunk.