Dual Registration - Cisco 8851 Administration Manual

SIP and NAT Configuration

Dual Registration

The phone always registers to both primary (or primary outbound) and alternate (or alternate outbound)
proxies. After registration, the phone sends out Invite and Non-Invite SIP messages through primary proxy
first. If there is no response for the new INVITE from the primary proxy, after timeout, the phone attempts
to connect with the alternate proxy. If the phone fails to register to the primary proxy, it sends an INVITE to
the alternate proxy without trying the primary proxy.
Dual registration is supported on a per-line basis. Three added parameters can be configured through web
user interface and remote provisioning:
• Alternate Proxy—Default is empty.
• Alternate Outbound Proxy—Default is empty.
• Dual Registration—Default is NO (turned off).
After you configure the parameters, reboot the phone for the feature to take effect.
Specify a value for primary proxy (or primary outbound proxy) and alternate proxy (or alternate outbound
Note
proxy) for the feature to function properly.
Dual Registration and DNS SRV Limitations
• When Dual Registration is enabled, DNS SRV Proxy Fallback or Recovery must be disabled.
• Do not use Dual Registration along with other Fallback or Recovery mechanisms. For example: Broadsoft
mechanism.
• There is no recovery mechanism for feature request. However, the administrator can adjust the
reregistration time for a prompt update of the registration state for primary and alternate proxy.
Dual Registration and Alternate Proxy
When the Dual Register parameter is set to No, Alternate Proxy is ignored.
Failover and Recovery Registration
• Failover—The phone performs a failover when transport timeout/failure or TCP connection failures; if
Try Backup RSC and Retry Reg RSC values are datafilled.
• Recovery—The phone attempts to reregister with the primary proxy while registered or actively connected
to the secondary proxy.
Auto register when failover parameter controls the failover behavior when there is an error. When this
parameter is set to yes, the phone re-registers upon failover or recovery.
Fallback Behavior
The fallback occurs when the current registration expires or Proxy Fallback Intvl fires.
If the Proxy Fallback Intvl is exceeded, all the new SIP messages go to primary proxy.
For example, when the value for Register Expires is 3600 seconds and Proxy Fallback Intvl is 600 seconds,
the fallback triggers 600 seconds later.
Cisco IP Phone 8800 Series Multiplatform Phones Administration Guide
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