AASTRA 6700i series, 9143, 9480i, 9480i CT SIP Administrator Guide EN - Manual (Page 670)

41-001343-01 Rev 03, Release 3.2.2 6-43
Configurable DNS Queries
The domain name system (DNS) is the way that Internet domain names are located and translated
into Internet Protocol addresses. A domain name is a meaningful and easy-to remember identifier
for an Internet address.
The lists of domain names and IP addresses are distributed throughout the Internet in a hierarchy
of authority within a database of records. There is usually a DNS server within close proximity to
your geographic location that maps the domain names in your Internet requests or forwards them
to other servers in the Internet.
The IP Phones may be configured to issue requests for DNS records using one of three methods. In
the first method, the IP phones issue requests for “A” records from the DNS server. In the second
method, the IP phones issue requests for “SRV” records from the DNS server. In the third method,
the IP phones issue requests for NAPTR records from the DNS server. However, the IP phones do
not use the NAPTR record to determine whether to use a secure or unsecure communication path
(see the following table for a description of each method).
When the IP phone accesses the IP network, it issues a DNS lookup request to find the IP address
and port and then waits for a response from the DNS service that provides the IP address and port.
You can configure the phone to use any one of these methods by entering the applicable v alue in
the configuration files:
Note: Whether or not the phone will operate/communicate in a secure or
unsecure mode is ONLY determined by the pre-provisioning of the
phone (i.e. the .cfg file).
Configuration
File Value DNS Server
Method Used
Description
0 A only The phone issues requests for “A” (Host IP Address) records from
the DNS server to get the IP address, and uses the default port
number of 5060.