Aastra Telecom 9143i Series User Manual

41-001160-03, Rev 00, Releaes 2.4

4-23

Configuring Network and Session Initiation Protocol (SIP) Features

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.

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

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.

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.

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