I've been doing this for the past year and a half. It's important to stay on the same network if you can, because of SLA's. The only issue I have run into is when my central office VPN device was having to do so much that the CPU utilization caused some packet loss, which resulted in poor quality voice. Just make sure you VPN devices can handle the encryption on the fly with minimal fuss.
Do you only have a Call Manager at the main site only(the site where there are 120 people?). The remote site that you mentioned (20 people), does it not have a call manager server locally? Also, which codec are you running between both sites? G.729a?
We have a Callmanager cluster at our main site and routers with SRST at the other sites. Unless you have a DSP resource, you have to use G.711, otherwise you will not be able to use things like conference calling and some voice mail systems.
I do this often. We have several people (including myself) at the end of ADSL circuits (forcing G.729a for that region). We have shared extensions (ie. rings in the office, rings at home...) very cool.
Today, I'm at the VON (Voice on Network) http://www.pulver.com/von conference at a hotel right now with Broadband, and spent the evening making phone calls using my Cisco IP Softphone using the Hotel's broadband connection... even with 200-300ms icmp/ping times, I was getting very good connections. A slight delay, but very usable. Nothing like using all the tools you have in the office on the road!
SIP traces provide key information in troubleshooting SIP Trunks, SIP
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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
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CUCM Database Replication is an area in which Cisco customers and
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