PointRed Telecom Ltd. MCRD-2458 Benutzerhandbuch
M i c r o R e d & M i c r o V i e w N M S U s e r M a n u a l v 1 . 0
Page 73
In the current version DHCP server configuration does not support dynamic
changing of the DHCP leases file. After an IP allocation you are able to see the
new record in the DHCP Leases dialog after approximately a 60 second delay.
changing of the DHCP leases file. After an IP allocation you are able to see the
new record in the DHCP Leases dialog after approximately a 60 second delay.
7.1.2.
Lease Time Strategies
One of the most common DHCP administration questions is, "What setting should
I give my lease times?" As with many networking questions, the answer is, "It
depends." The primary decision criterion is the desired frequency at which your
clients update their configuration data.
I give my lease times?" As with many networking questions, the answer is, "It
depends." The primary decision criterion is the desired frequency at which your
clients update their configuration data.
If you are using DHCP only for randomized address assignments, having longer
lease times will result in greater levels of stability. For example, if you use lease
duration times of one month or longer, a temporary server outage is not likely to
affect your normal operations much. However, if you are using DHCP for a
variety of system-configuration options (such as default DNS servers and static
routes), you will want to have shorter lease times so that changes to the network
are recognized quickly by the DHCP clients. In this case, having lease times that
are longer than a day or two can be problematic because clients that obtain a
new lease just before a critical infrastructure change is made will not recognize
this change until the lease expires or gets renewed.
lease times will result in greater levels of stability. For example, if you use lease
duration times of one month or longer, a temporary server outage is not likely to
affect your normal operations much. However, if you are using DHCP for a
variety of system-configuration options (such as default DNS servers and static
routes), you will want to have shorter lease times so that changes to the network
are recognized quickly by the DHCP clients. In this case, having lease times that
are longer than a day or two can be problematic because clients that obtain a
new lease just before a critical infrastructure change is made will not recognize
this change until the lease expires or gets renewed.
For dynamic environments, there are two common lease-duration strategies. The
first calls for leases to be renewed halfway through a working day (such as
having them expire every eight hours, which will cause them to be renewed after
four hours). Another strategy is to set the lease duration to a multiple of two and
a half times the working day (that is, 20 hours for an eight-hour working day),
causing the leases to completely expire overnight and thus be renegotiated every
morning. The former strategy works well on networks that keep their machines
running all of the time, while the latter strategy works well on networks where
systems are powered down or otherwise removed from the network at night.
first calls for leases to be renewed halfway through a working day (such as
having them expire every eight hours, which will cause them to be renewed after
four hours). Another strategy is to set the lease duration to a multiple of two and
a half times the working day (that is, 20 hours for an eight-hour working day),
causing the leases to completely expire overnight and thus be renegotiated every
morning. The former strategy works well on networks that keep their machines
running all of the time, while the latter strategy works well on networks where
systems are powered down or otherwise removed from the network at night.
Be forewarned, however, that both strategies expose the network to problems if
the DHCP server goes down or is on a remote network that is subject to outages.
If the DHCP clients are getting their lease data from a remote DHCP server that
is on the other side of a WAN link that is even minimally prone to failure, chances
are good that short lease times will result in at least a few failed lease renewals.
the DHCP server goes down or is on a remote network that is subject to outages.
If the DHCP clients are getting their lease data from a remote DHCP server that
is on the other side of a WAN link that is even minimally prone to failure, chances
are good that short lease times will result in at least a few failed lease renewals.
7.2.
Configuring a DHCP CLIENT
Configuration of the DHCP Client application is simple. The only requirement is
selection of the interface where the DHCP client will search for DHCP servers.
selection of the interface where the DHCP client will search for DHCP servers.
Similar to DHCP server configuration, multiple instances of DHCP client on
different interfaces are allowed.
different interfaces are allowed.