Aastra Telecom 41-001343-02 manual Domain Name System DNS Server Pre-caching Support

Advanced Operational Features

Examples

There are two ways to format the XML key URI:

For XML Post Messages

<ExecuteItem URI="<XML Key URI>" /> Example:

<ExecuteItem URI="Key: Line1" />

For XML Key Scripts

<URI><XML Key URI></URI>

Example:

<URI>Key: Line1</URI>

<SoftKey index="1">

<Label>Keypad1</Label>

<URI>Key: Line1</URI>

</SoftKey>

Domain Name System (DNS) Server Pre-caching Support

The IP phones now support the use of a local DNS host file to resolve DNS queries, and supports pre-provisioning of DNS SRV records. This feature allows administrators to configure the phone to download a text file which contains persistent DNS “A record” hostname to IP address mappings. In addition, support for persistent DNS “SRV records” has been added to permit SRV based high availability of services.

There are two methods used to configure DNS pre-caching on the IP phone:

•Configure a unix style “host” file used instead of a DNS “A query” to resolve hostnames to IP addresses. The host file is downloaded and cached on the IP phone.

•Configure DNS “SRV queries” for geographic redundancy and failover. The configured SRV entries are used to pre-load the DNS cache on the IP phone.

Both these methods are configurable using the configuration files only, and are primarily intended for use when a third party hosting provider delivers SIP services but does not have local access or control of the LAN side DNS infrastructure.

Note:

Time-to-Live (TTL) used in this feature is hard-coded for each server and not configurable.

Configuring DNS “Host File” Pre-caching from the Configuration Server

The DNS host file must reside on the same server as the configuration files (aastra.cfg/.tuz, etc.) and the filename to download is specified within the configuration.

Use the following parameter to configure the phone to use the host file for host IP address lookups.

Configuration Files

For the specific parameter you can set in the configuration files, see Appendix A, the section, “DNS Host File” on page A-214.

The following procedure is an example of how to use the “sip dns host file” parameter to configure DNS lookup pre-cach- ing from the configuration server.

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