Dns Caching - Mitel 6800 Series Administrator's Manual

Mitel 6800 Series SIP Phone Release 4.2.0 SP2 Administrator Guide
Notes:
1. 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.
2. If the DHCP servers do not have any of the Options (43, 66, 159, and 160) configured,
the phone's boot up process of will take approximately six more seconds.
3. In certain multiple DHCP server scenarios, due to the configuration of the servers
as well as the response time and speed of the servers, a DHCP offer with no
configuration server information may be accepted instead of an offer with
configuration server information.
For example, when three DHCP servers are available (the fastest with no
configuration server information defined, the second fastest with no configuration
server information defined but with an IP reserved for the phone, and the slowest
with configuration server information defined) the phone will initially select the offer
from the slowest server as it contains configuration server information. However,
the phone will then send a broadcast request, whereby the second fastest server
will reply with a NACK before the slowest server's ACK reply, causing the phone to
send another broadcast request and triggering the phone to change to a selecting
state. The fastest server will then reply with an ACK and, due to the state change,
the phone will accept the fastest server's offer.
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.
CONFIGURING NETWORK SETTINGS MANUALLY
If you disable DHCP on your phone, you need to configure the following network settings
manually:
• IP Address
• Subnet Mask
• Gateway
• Primary DNS
• Secondary DNS
Note: If you disable DHCP on the phone, the phone uses the TFTP protocol as the
default server protocol. If you want to specify a different protocol to use, see
"Configuration Server Protocol"
You can configure the network settings using the configuration files, the IP phone UI, or the
Mitel Web UI.
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on page 4-101.