• 720 Cisco IP Phones when using a ISR 3845

• call preservation
• auto-provisioning
• failover
• SRTP encryption

• All IOS SRST features except SRTP
• Paging
• Conferencing
• Hunt groups
• B-ACD
• Call park, call pickup, call pickup groups
• Overlay DN, softkey templates
• Cisco IP Communicator 2.0
• Cisco Unified Video Advantage 2.0
• Integrate with Cisco Unity with MWI at remote sites
• Does not support SIP or MGCP phones, use SIP SRST or MGCP Gateway Fallback instead.

• Configure COS following the instructions in Gateway COS
• Using the cor incoming command within the call-manager-fallback configuration mode, configure the complex corlists acting as “calling search spaces” to be incoming corlists assigned to the various phone DNs:

call-manager-fallback
  cor incoming InternalCSS default
  cor incoming LocalCSS 1 3001 - 3003
  cor incoming LDCSS 2 3004
  cor incoming IntlCSS 3 3010

<note>• In SRST version 2.0, available on Cisco IOS Release 12.2(8)T or later, the maximum number of cor incoming statements allowed under call-manager-fallback is 5 (plus the default statement).

• In SRST version 3.0, available on Cisco IOS Release 12.3(4)T or later, the maximum number of cor incoming statements allowed under call-manager-fallback is 20 (plus the default statement). </note>