3Com Switch 7750 Configuration Guide Guide

Global Address Pool-Based DHCP Server Configuration 563
segments that are previously specified. Currently, an address pool can contain only
one address segment, whose ranges are determined by the subnet mask.
To avoid IP address conflicts, the IP addresses to be dynamically assigned to DHCP
clients are those that are not occupied by specific network devices (such as
gateways and FTP servers).
The lease time can differ with address pools. But that of the IP addresses of the
same address pool are the same. Lease time is not inherited, that is to say, the
lease time of a child address pool is not affected by the configuration of the parent
address pool.
n
■ In the same DHCP global address pool, the network command can be
executed repeatedly. In this case, the new configuration overwrites the
previous one.
■ The dhcp server forbidden-ip command can be executed repeatedly. That is,
you can repeatedly configure IP addresses that are not dynamically assigned to
DHCP clients.
Configuring DNS
Services for the DHCP
Server
If a host accesses the Internet through domain names, DNS is needed to translate
the domain names into the corresponding IP addresses. To enable DHCP clients to
access the Internet through domain names, a DHCP server is required to provide
DNS server addresses while assigning IP addresses to DHCP clients. Currently, you
can configure up to eight DNS server addresses for a DHCP address pool.
You can configure domain names to be used by DHCP clients for address pools.
After you do this, the DHCP server provides the domain names to the DHCP clients
as well while the former assigns IP addresses to the DHCP clients.
Table 433 Configure to assign IP addresses dynamically
Operation Command Description
Enter system view system-view -
Create a DHCP address pool
and enter DHCP address pool
view
dhcp server ip-pool
pool-name
Required
By default, no DHCP address
pool is created
Set the IP address segment
whose IP address are to be
assigned dynamically
network ip-address [ mask
mask ]
Required
By default, no IP address
segment is set. That is, no IP
address is available for being
assigned
Configure the lease time
expired { day day [ hour
hour [ minute minute ] ] |
unlimited }
Optional
The default lease time is one
day
Return to system view quit -
Specify the IP addresses that
are not dynamically assigned
dhcp server forbidden-ip
low-ip-address [
high-ip-address ]
Optional
By default, all IP addresses in a
DHCP address pool are
available for being
dynamically assigned