Specifications

Configuring Cisco Unified SIP SRST Features Using Redirect Mode (for Version 3.0 Only)
Restrictions for Cisco Unified SIP SRST Features Using Redirect Mode
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Cisco Unified SIP SRST 4.0 System Administrator Guide
Restrictions for Cisco Unified SIP SRST Features Using Redirect
Mode
See the restrictions documented in the “Restrictions for Configuring Cisco Unified SIP SRST” section
in the “Cisco Unified SIP SRST Feature Overview” chapter.
Information About Cisco UnifiedSIP SRST Features Using
Redirect Mode
Cisco Unified SIP SRST provides backup to an external SIP proxy server by providing basic registrar
and redirect services. These services are used by a SIP IP phone in the event of a WAN connection outage
when the SIP phone is unable to communicate with its primary SIP proxy. The Cisco Unified SIP SRST
device also provides PSTN gateway access for placing and receiving PSTN calls.
To make maximum use of the Cisco Unified SIP SRST service, the local SIP IP phones should support
dual (concurrent) registration with both their primary SIP proxy or registrar and the Cisco Unified SIP
SRST backup registrar. Cisco Unified SIP SRST works for the following types of calls:
• Local SIP IP phone to local SIP phone, if the main proxy is unavailable.
• Additional services like class of restriction (COR) for local SIP IP phones to the outgoing PSTN.
For example, to block outgoing 1-900 numbers.
How to Configure Cisco Unified SIP SRST Features Using
Redirect Mode
This section contains the following procedures:
• Configuring Call Redirect Enhancements to Support Calls Between SIP IP Phones for Cisco Unified
SIP SRST, page 41 (required)
• Configuring Sending 300 Multiple Choice Support, page 43 (required)