Cisco SPA942 - Cisco - IP Phone User Manual

Configuring SIP, SPCP, and NAT
Configuring SIP
Cisco SPA and Wireless IP Phone Administration Guide 89
5
SIP Proxy Redundancy
An average SIP proxy server may handle tens of thousands of subscribers. A
backup server allows an active server to be temporarily switched out for
maintenance. Cisco phones support the use of backup SIP proxy servers to
minimize or eliminate service disruption.
A static list of proxy servers is not always adequate. If your user agents are served
by different domains, for example, you would not want to configure a static list of
proxy servers for each domain into every Cisco IP phone.
A simple way to support proxy redundancy is to configure a SIP proxy server in
the Cisco IP phone configuration profile. The DNS SRV records instruct the phones
to contact a SIP proxy server in a domain named in SIP messages. The phone
consults the DNS server. If configured, the DNS server returns an SRV record that
contains a list of SIP proxy servers for the domain, with their host names, priority,
listening ports, and so on. The Cisco IP phone tries to contact the hosts in the order
of their priority.
If the Cisco IP phone currently uses a lower-priority proxy server, the phone
periodically probes the higher-priority proxy and switches to the higher-priority
proxy when available.
RFC3311 Support
The Cisco SPA525G supports RFC3311, the SIP UPDATE Method.
Configuring SIP
SIP settings for the SPA and Wireless IP phones are configured for the phone in
general and for individual extensions. The following sections describe SIP
configuration.

Cisco SPA942 - Cisco - IP Phone Specifications

General

Brand	Cisco
Model	SPA942 - Cisco - IP Phone
Category	IP Phone
Language	English