Will you be using a VPN tunnel to access the Call Manager servers? This is recommended!
If so the configuration is somewhat the same as your internal network phones. DHCP requests for the individual phones can be forwarded across the VPN tunnel with a specific DHCP Scope for each VPN user. The phones DHCP address is singled out by the forwarding gateway address.
If you are not using VPN connectivity, which is not recommended
You would have to expose your Call Manager server(s) to the public Internet. Skinny Port: 2000 and H323 Port: 1720 (if used) as well as some others. Also you would need to register your Call Manager servers in Public DNS. You could need to set static IP addresses on the phones or have a local DHCP server at the remote end. This configuration will only work when not using NAT. In other words your internal address will need to be publicly routable addresses behind the PIX.
Could you post more info about your configuration?
Specific topology end to end…
How much bandwidth is available for the remote phones?
What Security concerns do you have for Call Manager servers?
