Installation guide
Advanced Operational Features
6-37 41-001561-00 REV00 – 10.2014
If all three servers with priority 10 are unavailable, the next highest priority record is selected, in this case backupbox.
This could be a server in another physical location.
The server entries in the aastra.cfg file can use DNS hostnames or can use IP addresses. If hostnames are used, any pre-
cached DNS A records via the host file mechanism are used before resorting to live DNS query if there is no local match.
For example, the following hostfile.text uses IP addresses that are used in the DNS server queries:
hostfile.txt
192.168.2.3 bigbox.example.com
192.168.3.4 smallbox1.example.com
192.168.8.1 smallbox2.example.com
47.28.05.69 backupbox.example.com
Use the following procedure in the configuration files to configure DNS server query support for the phones.
Use the following procedure to configure DNS SRV record pre-caching.
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.
Configuration Files
For the specific parameter you can set in the configuration files, see Appendix A, the section, “DNS Server Query” on pageA-229.
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.