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DHCP Server Administration

Issue 1 January 2008 53

- Option 51 - DHCP lease time.

If this option is not received, the DHCPOFFER is not be accepted. Avaya

recommends a lease time of six weeks or greater. If this option has a value of

FFFFFFFF hex, the IP Address lease is assumed to be infinite as per RFC 2131,

Section 3.3, so that renewal and rebinding procedures are not necessary even if

Options 58 and 59 are received. Expired leases cause the telephones to reboot.

Avaya recommends providing enough leases so an IP Address for an IP telephone

does not change if it is briefly taken offline.

Note:

Note: The DHCP standard states that when a DHCP lease expires, the device should

immediately cease using its assigned IP Address. If the network has problems

and the only DHCP server is centralized, the server is not accessible to the given

telephone. In this case the telephone is not usable until the server can be

reached.

Avaya recommends, once assigned an IP Address, the telephone continues

using that address after the DHCP lease expires, until a conflict with another

device is detected. As Table 9:

Avaya Agent Deskphone 16CC Customizeable

System Parameters indicates, the system parameter DHCPSTD allows an

administrator to specify that the telephone will either:

a). Comply with the DHCP standard by setting DHCPSTD to “1”, or

b). Continue to use its IP Address after the DHCP lease expires by setting

DHCPSTD to “0.”

The latter case is the default. If the default is invoked, after the DHCP lease

expires the telephone sends an ARP Request for its own IP Address every five

seconds.

The request continues either forever, or until the telephone receives an ARP

Reply. After receiving an ARP Reply, the telephone displays an error message,

sets its IP Address to 0.0.0.0, and attempts to contact the DHCP server again.

- Option 52 - Overload Option, if desired.

If this option is received in a message, the telephone interprets the sname and file

fields in accordance with IETF RFC 2132,

Section 9.3, listed in Appendix B:

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Avaya 16CC Betriebsanweisung Seite 53