Aastra Telecom 41-001343-02 manual Multiple Dhcp Servers, DNS Caching

Network Settings

Configuring a Download Precedence Using the Aastra Web UI

Use the following procedure to configure a download precedence using the Aastra Web UI.

Aastra Web UI

1.Click on Advanced Settings->Network->Advanced Network Settings.

2.In the “DHCP Download Options” field, select “Disabled” from the list of options.

Note:

In the Aastra Web UI, the “Disabled” download option performs the same function as the “-1” in the configuration files (ignores DHCP options).

3.Click Save Settings to save your setting.

4.Select Operation->Reset, and click Restart to reboot the phone.

Multiple DHCP Servers

The IP Phones can receive messages from multiple DHCP servers.

After the phone receives its first DHCP message, it listens for a specific time period, for more DHCP messages. If the first DHCP offer contains configuration server information (Options 43, 66, 159 or 160), then the phone times out and contin- ues using the first DHCP offer, without listening for more DHCP offers. If the first DHCP message contains no configuration server information, the phone continues to listen for other DHCP messages. If the second DHCP message contains config- uration server information and other conditions, the phone chooses the second DHCP message over the initial DHCP mes- sage.

Note:

If the DHCP Download Options parameter is enabled with a value (Option 43, Option 66, Option 159, or Option 160), the phone checks the override option setting before timing out.

Warning!

Users currently using multiple DHCP servers on a single network could be affected by this feature.

DNS Caching

The IP phones have the ability to cache DNS requests as referenced in RFC1035 and RFC2181. The phone caches DNS lookups according to the TTL field, so that the phone only performs another lookup for an address when the TTL expires.

41-001343-02 REV04 – 05.2014 4-17