Configuring SIP, SPCP, and NAT
Configuring SIP
Cisco Small Business SPA300 Series, SPA500 Series, and WIP310 IP Phone Administration Guide 120
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Make Call Without Reg Enables making outbound calls without successful 
(dynamic) registration by the phone. If set to no, the dial 
tone plays only when registration is successful.
Defaults to no.
Register Expires Defines how often the phone renews registration with 
the proxy. If the proxy responds to a REGISTER with a 
lower expires value, the phone renews registration 
based on that lower value instead of the configured 
value.
If registration fails with an “Expires too brief” error 
response, the phone retries with the value specified in 
the Min-Expires header of the error.
Defaults to 60 seconds.
Ans Call Without Reg If enabled, the user does not have to be registered with 
the proxy to answer calls.
Defaults to no. 
Use DNS SRV Enables DNS SRV lookup for the proxy and outbound 
proxy.
Defaults to no.
DNS SRV Auto Prefix Enables the phone to automatically prepend the proxy or 
outbound proxy name with _sip._udp when performing a 
DNS SRV lookup on that name.
Defaults to no.
Proxy Fallback Intvl Sets the delay after which the phone retries from the 
highest priority proxy (or outbound proxy) after it has 
failed over to a lower priority server. 
The phone should have the primary and backup proxy 
server list via DNS SRV record lookup on the server 
name. It needs to know proxy priority; otherwise, it does 
not retry.
Defaults to 3600 seconds.
Parameter  Description