We have CME 4.0 at central site and VPN tunnels for remote sites. Can I install Cisco 7961G-GE IP phones at remote sites withouth installing CME Router? Will the phones register with CME 4.0 using VPN tunnel connected to the Central site?
Actually with CME 4.0 teleworker remote phone are now supported over WAN, with previsous versions of CME the following restrictions applied:
Cisco TAC will not handle any voice or signaling issues for remote IP phones, unless the same issue can be replicated for LAN phones.
E911 or emergency calls are not supported from remote IP phones.
All calls made to and from remote IP phones must use G.711. Cisco Unified CME does not support the ability to specify G.729 codec for remote IP phones.
For inbound or outbound calls, remote IP phones cannot fail and go over to a PSTN connection. Remote phones must use the WAN for all calls, even if available bandwidth is not sufficient to guarantee voice quality.
Remote IP phones do not support Network Address Translation (NAT). All Cisco Unified CME phones must use IP addresses that are can be routed to and from Cisco Unified CME. Remote IP phones must be able to access the IP addresses that are used for all other local and remote phones. On prvisous versions the main obstecles were the following:
All PSTN access is through the central site only. PSTN termination at the remote site is not supported.
Cisco Unified CME does not support Call Admission Control (CAC) for remote SCCP phones, so voice quality can degrade if a WAN link is oversubscribed. High-bandwidth data applications used over a WAN can cause degradation of voice quality for remote IP phones.
With 4.0 you can now specify g.729 codec at the ephone level, check out the link for more details:
Yes, as long as there is proper routing the phone will register just fine. Just make sure IP phone gets TFTP address either from DHCP option 150 or manually and that should be it.
The problem will be QoS if you have no control over subnets that VPN tunnel traverses. And maybe bandwidth issue. For some reason I could not make remote phone to use G729 codec. So you maybe it have be forced to use G711. But I have not played with it much.
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