Digi Connect WAN Series User Manual page 42

Digi Connect WAN Family web interface
DHCP terminology
Some key terms involved in configuring a DHCP server include:
scope
A scope is the full consecutive range of possible IP addresses for a network and typically defines a
single physical subnet on your network, where DHCP services are offered. A scope is the primary way
for the DHCP server to manage distribution and assignment of IP addresses and related configuration
parameters to its clients on the network.
exclusion range
An exclusion range is a limited sequence of IP addresses within a scope, excluded from DHCP service
offerings. Exclusion ranges assure that any addresses in these ranges are not offered by the server to
DHCP clients on your network.
address pool
After the scope is defined and exclusion ranges are applied, the remaining addresses form the
available address pool within the scope. The addresses in this pool are available for dynamic
assignment by the server to DHCP clients on your network.
lease
A lease is the length of time that the DHCP server specifies, during which a client host can use an
assigned IP address. When the DHCP server grants a lease to a client, the lease is active.
Before the lease expires, the client typically needs to renew its address lease assignment with the
DHCP server. A lease becomes inactive when it expires or it is deleted at the server, or if the client
actively releases the lease. The duration of a lease determines when it will expire and how often the
client needs to renew it with the DHCP server in order to retain the lease.
A DHCP server never grants a lease to its own address. There is no need for its own address to be in
the exclusion range; the DHCP server simply protects its address from being offered.
grace period
When a DHCP client actively releases a lease, or when the lease expires without being renewed by the
client, the DHCP server does not immediately delete the lease record and return the associated IP
address to the available address pool. A grace period is the interval of time for which the lease record
is retained before the DHCP server automatically deletes the record from its lease list, thereby
making the IP address available for lease assignment to another client. The grace period is not a
configurable value.
For more about the grace period and what it means when the DHCP server is running, see
manage the current DHCP
reservation
You may use a reservation to create a permanent address lease assignment by the DHCP server.
Reservations assure that a specified hardware device on the subnet can always use the same IP
address. Address lease reservations associate a specific IP address with a specific client's Ethernet
MAC address.
options
Options are other client configuration parameters that the DHCP server can assign when serving
leases to DHCP clients. Most options are defined in RFC 2132. The DHCP server in the Digi device
supports a limited set of options:
Option 3: Routers on Subnet
n
Option 6: DNS Servers
n
Addresses in the DHCP server settings
The IP address and subnet mask of the DHCP server's scope are the static IP configuration settings
for the Digi Connect WAN Family itself.
Digi Connect WAN Family User Guide
leases.
Configuration through the web interface
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