Avaya one-X 9600 Series Administrator's Manual page 60

Server Administration
Note:
The DHCP standard states that when a DHCP lease expires, the device should
Note:
immediately cease using its assigned IP Address. However, if the network has
problems and the only DHCP server is centralized or if the DHCP server itself
has problems, the telephone will not receive responses to its request for a
renewal of the lease. In this case the telephone will not be usable until the server
can respond.
Avaya recommends that 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
System Parameters
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 continues to broadcast DHCPREQUEST messages for its
current IP address, and it sends an ARP Request for its own IP Address every
five seconds.
The messages continue to be sent until the telephone receives a DHCPACK, a
DHCPNAK, or an ARP Reply. After receiving a DHCPNAK, or 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.
Depending on the DHCP application you choose, be aware that the application
most likely does not immediately recycle expired DHCP leases. An expired lease
might remain reserved for the original client a day or more. For example,
Windows NT
period protects a lease for a short time. If the client and the DHCP server are in
two different time zones, the clocks of the computers are not in sync, or the client
is not on the network when the lease expires, there is time to correct the situation.
The following example shows the implication of having a reservation period: Assume
two IP Addresses, therefore two possible DHCP leases. Assume three IP
Deskphones, two of which are using the two available IP Addresses. When the lease
for the first two telephones expires, the third telephone cannot get a lease until the
reservation period expires. Even if the other two telephones are removed from the
network, the third telephone remains without a lease until the reservation period
expires.
- 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
- Option 58 - DHCP lease renew time.
If not received or if this value is greater than that for Option 51, the default value of T1
60 9600 Series IP Deskphone Administrator Guide Release 6.0
Table 12: 9600 Series IP Telephone Customizable
indicates, the system parameter DHCPSTD allows an
®
DHCP reserves expired leases for about one day. This reservation
Appendix B: Related Documentation.