Advanced Operational Features
6-40
41-001343-02 REV05 – 07.2014
Configuring DNS SRV Record Pre-caching
Configurable DNS Maximum Cache TTL
Administrators can manually set the DNS maximum cache TTL settings for both negative and positive responses on the
phone by defining the “
sip dns cache negative max ttl
” and “
sip dns cache positive max ttl
” parameters in the config-
uration files. Setting these parameters will help alleviate issues regarding the phone not considering the DNS retry time
settings defined by the DNS server.
Configuring the DNS Maximum Cache TTL
Use the following procedure to configure the DNS maximum cache TTL settings.
1.
Using a text-based editing application, open the
aastra.cfg
file.
2.
Enter the parameter, “
sip dns srvX name
”, where “X” is a value from 1 to 4.
Enter a value for the DNS SRV service URI. For example:
sip dns srv1 name: _sip._udp.example.com
3.
Enter the parameter, “
sip dnx srvX priority
, where “X” is a value from 1 to 4.
Enter a value for the DNS server priority. Valid values are 0 to 65535. Default is 0. For example:
sip dns srv1 priority: 10
After this parameter is downloaded from the configuration server to the phone, the phone uses the DNS server with the lowest numbered
priority first to perform DNS lookups.
4.
Enter the parameter, “
sip dnx srvX weight
, where “X” is a value from 1 to 4.
Enter a value for the DNS server weight. Valid values are 0 to 65535. Default is 0. For example:
sip dns srv1 weight: 60
Note:
The “sip dns srv1 weight” parameter must be configured but will be supported in a future release.
5.
Enter the parameter, “
sip dnx srvX port
, where “X” is a value from 1 to 4.
Enter a value for the port number on the target host. Valid values are 0 to 65535. Default is 0. For example:
sip dns srv1 port: 5060
6.
Enter the parameter, “
sip dnx srvX target
, where “X” is a value from 1 to 4.
Enter a value for the DNS server target. Valid values are the host name or a fully qualified domain name. For example:
sip dns srv1 target: bigbox.example.com
7.
Save and close the file.
8.
Place the
aastra.cfg
file on the configuration server and download to the phones.
Configuration Files
For the specific parameter you can set in the configuration files, see Appendix A, the section,