3Com 4500 PWR 26-Port Configuration Manual page 471

The IP addresses statically bound in interface address pools and the interface IP addresses must
be in the same network segment.
There is no limit to the number of IP addresses statically bound in an interface address pool, but
the IP addresses statically bound in interface address pools and the interface IP addresses must
be in the same segment.
An IP address can be statically bound to only one MAC address or one client ID. A MAC address or
client ID can be bound with only one IP address statically.
The IP address to be statically bound cannot be an interface IP address of the DHCP server;
otherwise the static binding does not take effect.
Configuring the dynamic IP address allocation mode
As an interface-based address pool is created after the interface is assigned a valid unicast IP address,
the IP addresses contained in the address pool belong to the network segment where the interface
resides in and are available to the interface only. So specifying the range of the IP addresses to be
dynamically assigned is unnecessary.
To avoid address conflicts, the DHCP server automatically excludes IP addresses (used by the gateway,
FTP server and so forth) specified with the dhcp server forbidden-ip command from dynamic
allocation.
To avoid IP address conflicts, the IP addresses to be dynamically assigned to DHCP clients are those
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.
Follow these steps to configure the dynamic IP address allocation mode:
To do...
Enter system view
Configure for
the current
interface
Configure
the lease
time
Configure
multiple
interfaces in
system view
Specify the IP addresses
that are not dynamically
assigned
Use the command...
system-view
interface interface-type
interface-number
dhcp server expired { day day
[ hour hour [ minute minute ] ] |
unlimited }
quit
dhcp server expired { day day
[ hour hour [ minute minute ] ] |
unlimited } { interface
interface-type interface-number
[ to interface-type
interface-number ] | all }
dhcp server forbidden-ip
low-ip-address [ high-ip-address ]
39-18
Remarks
—
Optional
The default lease time is one
day.
Optional
By default, all IP addresses in a
DHCP address pool are
available for being dynamically
assigned.