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Configuring Your System
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When a phone is configured with a DNS server, it will behave as follows by
default:
• An initial attempt to resolve a hostname that is within the static DNS
cache, for example to register with its SIP registrar, results in a query to the
DNS.
• If the initial DNS query returns no results for the hostname or cannot be
contacted, then the values in the static cache are used for their configured
time interval.
• After the configured time interval has elapsed, a resolution attempt of the
hostname will again result in a query to the DNS.
• If a DNS query for a hostname that is in the static cache returns a result,
the values from the DNS are used and the statically cached values are
ignored.
When a phone is not configured with a DNS server, it will behave as follows
• An attempt to resolve a hostname that is within the static DNS cache will
always return the results from the static cache.
Support for negative DNS caching as described in RFC 2308 is also provided
to allow faster failover when prior DNS queries have returned no results from
the DNS server. For more information, go to
http://tools.ietf.org/html/rfc2308 .
Configuration changes can be performed centrally at the boot server:
Configuration File Examples
Example 1
This example shows how to configure static DNS cache using A records IP
addresses in SIP server address fields.
When the static DNS cache is not used, the sip.cfg configuration would look
as follows:
reg.1.address="1001"
reg.1.server.1.address="172.23.0.140"
reg.1.server.1.port="5075"
Central
(boot server)
Configuration file:
sip.cfg
Specify DNS NAPTR, SRV, and A records for use when the phone is
not configured to use a DNS server.
• For more information, refer to DNS Cache <dns/> on page A-100.
Polycom recommends that you create another file with your organization’s
modifications. If you must change any Polycom templates, back them up first.
For more information, refer to the “Configuration File Management on SoundPoint
IP Phones” whitepaper at www.polycom.com/support/voice/.