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Advanced Operational Features
6-38 41-001343-02 REV04 – 05.2014
In the following example, both the priority and weight fields are used to provide a combination of load balancing and
backup service.
Example
sip dns srv1 name: _sip._udp.example.com
sip dns srv1 priority: 10
sip dns srv1 weight: 60
sip dns srv1 port: 5060
sip dns srv1 target: bigbox.example.com
sip dns srv2 name: _sip._udp.example.com
sip dns srv2 priority: 10
sip dns srv2 weight: 20
sip dns srv2 port: 5060
sip dns srv2 target: smallbox1.example.com
sip dns srv3 name: _sip._udp.example.com
sip dns srv3 priority: 10
sip dns srv3 weight: 20
sip dns srv3 port: 5060
sip dns srv3 target: smallbox2.example.com
sip dns srv4 name: _sip._udp.example.com
sip dns srv4 priority: 20
sip dns srv4 weight: 10
sip dns srv4 port: 5060
sip dns srv4 target: backupbox.example.com
The first three records (SRV 1, 2, and 3) share a priority of 10, so the weight field's value is used by the phones to load bal-
ance across the three target host names.
Bigbox will get 60% of the load, and smallbox1 and smallbox2 will each get 20% load.
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.
Configuration Files
For the specific parameter you can set in the configuration files, see Appendix A, the section, “DNS Server Query” on pageA-214.