I've found this info on the Cisco site regarding the UC520:
Virtual Private Networking
VPNs carry private data over a public network and extend remote access to users over a shared infrastructure. Maintaining the same security and management policies as private networks, VPNs are the most cost-effective means of establishing point-to-point connections between remote users and a central network. VPNs have been the fastest-growing form of network connectivity, and Cisco takes this approach to a new level by making VPN functions an integral part of the Cisco Unified Communications family of products. The Cisco Unified Communications 500 Series supports a maximum of 10 VPNs and includes built-in hardware-based encryption acceleration that offloads IP security (IPSec), Advanced Encryption Standard (AES), Data Encryption Standard (DES), and Triple DES (3DES) encryption and VPN processes to provide increased VPN throughput on the Cisco Unified Communications 500 Series platform. The platform also supports SSL (Secure Sockets Layer) VPN .
Does this mean 10 site to site VPN tunnels or 10 remote VPN clients?
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The short answer is that you don't.... That isn't entirely true while at
the same time it kind of is, but for the most part you don't configure
the softkeys. You enable or disable them via TCL. Here is the long
answer. Be sure to read the whole thing or e...
Topology: IP Phone > Switches > Microsoft NPS setup to forward 802.1x
proxy to > ISE 2.1 patch 3 Authentication: EAP-TLS using Cisco MIC SANs
Phone Models 802.1X support? 802.1x flavor Addtl Comment EAP-MD5 EAP-TLS
Cisco 3905 Y Y N Cisco 6911 Y Y N Cisco ...