Aastra Telecom 41-001343-02 manual Configuration Server Redundancy via DNS a Records, Limitation

Configuration Methods

With this configuration, on the Web UI, the "sip proxy ip" and "sip registrar ip” parameters cannot be modified (they are grayed out), and the value is "pbx.aastra.com" since <model>.cfg has overwritten aastra.cfg.

The "sip proxy port" and "sip registrar port" parameters can be modified through Web UI because <mac>.cfg has over- written <model>.cfg and aastra.cfg. On the Web UI, the value for these parameters is 5064.

Configuration Server Redundancy via DNS A Records

The phone sends a DNS query and in the DNS response, it accepts the first server IP address and contacts that server, ignoring any additional IP addresses in the response. This allows service providers to manage load balancing (via the DNS server putting different records first on each request), but does not provide redundancy.

The phones also provide support of multiple IP addresses being returned for the DNS lookup for server redundancy via multiple DNS A record entries. The phone tries to contact the first server address it receives, but if this fails, it now tries to contact the second server address, etc.

This feature supports all the download protocols (TFTP, FTP, HTTP, and HTTPS).

Notes:

•Once the phone has failed over to a redundant server, it continues to use that server for all other server-related proc- esses on the phone (i.e., firmware upgrades from the Web UI, boot-up process, etc.).

•If a server fails while downloading a file(s) to the phone, the phone performs the discovery process of finding a redundant server that is available. When the boot is complete on the redundant server, the phone tries to download the file(s) again from the previous server. The check-sync process also performs the same way when a server fails.

•The “Skip” softkey displays in the event of a network outage, the user can skip the configuration download and con- tinue the boot.

•All server failovers and failed server IP addresses are logged in the “Error Messages” page on the IP Phone UI at Options->PhoneStatus->Error Messages.

Limitation

In certain cases, the TFTP Protocol cannot distinguish between “server down” and “no file on server” error messages; therefore, the failover in these instances may fail.

41-001343-02 REV04 – 05.2014 2-17