Aastra 9143i Series Administrator's Manual page 207

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
continues 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 configuration server information and other conditions, the phone chooses
the second DHCP message over the initial DHCP message.
IMPORTANT NOTE
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 according to 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.
41-001160-03 Rev 00, Release 2.5
Configuring Network and Session Initiation Protocol (SIP) Features
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.
Network Settings
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