You can set up a VPN (or purchase a dedicated point-to-point link) and link your CallMans together.
Set the remote sites up as subscribers and one of the CCMs in your central site as the Publisher. In the device pool for the phones, then you just specify the desired CallManager to register with as the CallManager in your central site (the subscriber in your central site preferably), and a secondary CallManager in the local site. You may want to specify a third CallManager for your phones to fall back to if necessary.
With that said, keep in mind that if your remote link goes down, the phones would re-register with the local CallManager, then when they detected the remote CallManager was up, they'll re-register with the remote server and could swamp your link.
SIP traces provide key information in troubleshooting SIP Trunks, SIP
endpoints and other SIP related issues. Even though these traces are in
clear text, these texts can be gibberish unless you understand fully
what they mean. This document attempts to br...
Please find the attached HTML document, download and open it on your PC.
This provides an easy to use form where you simply answer a few
questions and it will render the proper jabber-config.xml file for you
to copy/paste. There is built in logic to verif...
CUCM Database Replication is an area in which Cisco customers and
partners have asked for more in-depth training in being able to properly
assess a replication problem and potentially resolve an issue without
involving TAC. This document discusses the bas...