3Com 4500 PWR 26-Port Configuration Manual page 455

T ypes of address pool
The address pools of a DHCP server fall into two types: global address pool and interface address pool.
A global address pool is created by executing the dhcp server ip-pool command in system view.
It is valid on the current device.
If an interface is configured with a valid unicast I
address pool for the interface by executing the dhcp select interface command in interface view.
The IP addresses an interf
resides in and are available to the interface only.
S tructure of an address pool
The address pools of a DHCP server are hierarchically organized in a tree-like structure. The root holds
the IP address of the natural network segment, the branches hold the subnet IP addresses, and the
leaves holds the IP addresses that are manually bound to specific clients. The address pools that are of
the same level are sorted by their configuration precedence order. Such a structure enables
configurations to be inherited. That is, the configurations of the natural network segment can be
inherited by its subnets, whose configura
parameters that are common to the whole network segment or some subnets (such as domain
you just need to configure them on the network segment or the corresponding subnets. The following is
the details of configuration inheritance.
1) A newly created child address pool inherits the configurations of its parent address pool.
2) For an existing parent-c
parent address pool:
The child address pool inherits the new config
the child address pool.
The child address pool does not inherit the new configuration if there is already a corresponding
config uration on the child address pool.
The IP address lease does not enjoy the inheritance attribute.
Principles of address pool selection
Th DHCP server observes the following principles to select an address pool to assign an IP address to e
a client:
1) If the receiving interface works in the global address pool mode, the DHCP server assigns an IP
address from the global address pool to the DHCP client.
2) If the receiving interface works in the interface address pool mode, the DHCP server assigns an IP
address from the interfa
there is no available IP address in the interface address pool, the DHCP server selects an IP
address from the global address pool that contains the interface address pool's network segment
for the client.
The DHCP server assigns an IP address to the client in the following order from an interface address
poo l or a global address pool:
ace address pool holds belong to the network segment the interface
tions in turn can be inherited by their client address. So, for the
hild address pool pair, when you performs a new configuration on the
uration if there is no corresponding configuration on
ce address pool to the DHCP client directly connected to the interface. If
39-2
P address, you can create an interface-based
name),