Cisco Unified SCCP and SIP SRST Feature Overview
Cisco Unified SIP SRST
21
Cisco Unified SCCP and SIP SRST System Administrator Guide
OL-13143-04
Version 4.1
12.4.(15)T
•
Cisco Unified SRST does not support BLF speed-dial notification, call forward all
synchronization, dial plans, directory services, or music-on-hold (MOH).
•
Prior to SIP phone load 8.0, SIP phones maintained dual registration with both
Cisco Unified Communications Manager and Cisco Unified SRST simultaneously.
In SIP phone load 8.0 and later versions, SIP phones use keepalive to maintain a
connection with Cisco Unified SRST during active registration with
Cisco Unified Communications Manager. Every two minutes, a SIP phone sends a
keepalive message to Cisco Unified SRST. Cisco Unified SRST responds to this
keepalive with a 404 message. This process repeats until fallback to
Cisco Unified SRST occurs. After fallback, SIP phones send a keepalive message
every two minutes to Cisco Unified Communications Manager while the phones
are registered with Cisco Unified SRST. Cisco Unified SRST continues to support
dual registration for SIP phone loads older than 8.0.
•
Enhanced 911 Services for Cisco Unified SRST does not interface with the
Cisco Emergency Responder.
•
The information about the most recent phone that called 911 is not preserved after
a reboot of Cisco Unified SRST.
•
Cisco Emergency Responder does not have access to any updates made to the
emergency call history table when remote IP Phones are in Cisco Unified SRST
fallback mode. Therefore, if the PSAP calls back after the Cisco Unified IP Phones
register back to Cisco Unified Communications Manager,
Cisco Emergency Responder will not have any history of those calls. As a result,
those calls will not get routed to the original 911 caller. Instead, the calls are routed
to the default destination that is configured on Cisco Emergency Responder for the
corresponding ELIN.
•
For Cisco Unified Wireless 7920 and 7921 IP Phones, a caller’s location can only
be determined by the static information configured by the system administrator. For
more information, see
Precautions for Mobile Phones
in
Configuring Enhanced
911 Services
.
•
The extension numbers of 911 callers can be translated to only two emergency
location identification numbers (ELINs) for each emergency response location
(ERL).
•
Using ELINs for multiple purposes can result in unexpected interactions with
existing Cisco Unified SRST features. These multiple uses of an ELIN can include
configuring an ELIN for use as an actual phone number (ephone-dn, voice register
dn, or FXS destination-pattern), a Call Pickup number, or an alias rerouting
number. For more information, see
Multiple Usages of an ELIN
in
Configuring
Enhanced 911 Services
.
•
There are a number of other ways that your configuration of Enhanced 911 Services
can interact with existing Cisco Unified SRST features and cause unexpected
behavior. For a complete description of interactions between Enhanced 911
Services
and existing Cisco Unified SRST features, see the
“Interactions with
Existing Cisco Unified SIP SRST Features” section on page 106
.
Table 2
Restrictions from Cisco SIP SRST from the Present Version to Version 3.0(continued)
Cisco Unified SRST
Version
Cisco IOS
Release
Restrictions
