Information Technology Reference
In-Depth Information
When a client initializes its IP networking, it always attempts to renew its old address. If
the client has time left on the lease, it continues to use the lease until its end. If the client is
unable to get a new lease by that time, all IP functions stop until a new, valid address can
be obtained.
DHCP Lease Release
Although leases can be renewed repeatedly, at some point they might run out. Furthermore,
the lease process is “at will.” That is, the client or server can cancel the lease before it ends.
In addition, if the client doesn't succeed in renewing the lease before it expires, the client
loses its lease and reverts to APIPA. This release process is important for reclaiming extinct
IP addresses used by systems that have moved or switched to a non-DHCP address.
Advantages and Disadvantages of DHCP
DHCP was designed from the start to simplify network management. It has some
significant advantages, but it also has some drawbacks.
Advantages of DHCP
The following are advantages of DHCP:
■
Configuration of large and even midsized networks is much simpler. If a DNS server
address or some other change is necessary to the client, the administrator doesn't have
to touch each device in the network physically to reconfigure it with the new settings.
■
Once you enter the IP configuration information in one place—the server—it's auto-
matically propagated to clients, eliminating the risk that a user will misconfigure some
parameters and require you to fix them.
■
IP addresses are conserved because DHCP assigns them only when requested.
■
IP configuration becomes almost completely automatic. In most cases, you can plug
in a new system (or move one) and then watch as it receives a configuration from the
server. For example, when you install new network changes, such as a gateway or DNS
server, the client configuration is done at only one location—the DHCP server.
■
It allows a preboot execution environment (PXE) client to get a TCP/IP address from
DHCP. PXE clients (also called Microsoft Windows Deployment Services [WDS]
clients) can get an IP address without needing to have an operating system installed.
This allows WDS clients to connect to a WDS server through the TCP/IP protocol and
download an operating system remotely.
Disadvantages of DHCP
Unfortunately, there are a few drawbacks with DHCP:
■
DHCP can become a single point of failure for your network. If you have only one
DHCP server and it's not available, clients can't request or renew leases.
Search WWH ::
Custom Search