A. Cisco SR 500 in secure router mode， acting as a front end for Cisco Unified Communications 500
B. centralized Cisco Unified Communications Manager BE with Cisco Unified Communications 500 in SRST mode
C. Cisco SR 500 teleworker with Cisco Unified Communications 500 as VPN server
D. multi-site VPN with Cisco Unified Communications 500 platforms
E. redundant Cisco Unified Communications 500 with primary-to-backup failover
F. Cisco Unified Communications 500 to Cisco Unified Communications Manager SIP trunk