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22-5
Cisco CNS Network Registrar User’s Guide
OL-6240-02
Chapter 22 Advanced DHCP Server Properties
Defining Advanced Server Parameters
Step 1 In the local cluster Web UI, click DHCP, then DHCP Server to open the Manage DHCP Serve page.
max-dhcp-responses set/
unset
Controls the number of response buffers that the DHCP server
allocates for responding to DHCP clients and performing failover
communication between DHCP partners.
In a non-failover deployment, the default setting of twice the
number of request buffers is sufficient. In a failover deployment, you
can increase this so that it is four times the number of request
buffers. In general, increasing the number of response buffers is not
harmful, while reducing it to below the previously recommended
ratios might be harmful to server responsiveness.
Some log messages that might trigger a change in this value are:
4721 DHCP ERROR "DHCP has used all xx response packets. A
request was dropped and they will continue to be dropped
if no responses are available."
5289 DHCP WARNING "DHCP has used xx of yy response
packets. Requests will be dropped if no responses are
available."
Required. The default is 1000.
max-ping-packets set/
unset
Controls the number of buffers that the server has available to
initiate Ping requests to clients. If you enable the Ping address
before offering it option at the scope level, packet buffers are used
to send and receive ICMP messages. If you enable pinging, you
should have enough ping packets allocated to handle the peak load
of possible ping requests. The default is 500 ping packets.
hardware-unicast enable/
disable
Controls whether the DHCP server sends unicast rather than
broadcast responses when a client indicates that it can accept a
unicast. This feature is only available on Windows NT, Windows
2000, and Solaris platforms; other operating systems broadcast
instead. The default is enabled.
defer-lease-extensions enable/
disable
Controls whether the DHCP server extends leases that are less than
half expired. This is a performance tuning attribute that helps
minimize the number of disk writes to the lease state database. The
default is checked or true. This means that a client renewing a lease
less than halfway through can get the remaining part of it only and
not be extended. See the “Deferring Lease Extensions” section on
page 22-6.
last-transaction-time-
granularity
set/
unset
Specifies the number of seconds that guarantees the last transaction
time to be accurate. This is a performance tuning attribute whereby
the server avoids frequent disk writes to the lease state database by
ignoring duplicate client activity (such as renews) within the set
granularity. Do not set this lower than 30 seconds. For optimal
performance, set it to a value that is greater than half the lease
interval. The default is 60 seconds.
Table 22-1 DHCP Advanced Parameters (continued)
Advanced Parameter Action Description