3Com Switch 7754, Configuration Manual

Page: 594 / 940

594 C
HAPTER
57: DHCP S
ERVER
C
ONFIGURATION
segment or some subnets (such as domain name), 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-child address pool pair, when you perform a new
configuration on the parent address pool:
■
The child address pool inherits the new configuration if there is no
corresponding configuration on the child address pool.
■
The child address pool does not inherit the new configuration if there is already
a corresponding configuration on the child address pool.
DHCP IP Address
Preferences
Interfaces of the DHCP server can work in the global address pool mode or in the
interface address pool mode. If the DHCP server works in the interface address
pool mode, it picks IP addresses from the interface address pools and assigns them
to the DHCP clients. If there is no available IP address in the interface address
pools, the DHCP server picks IP addresses from its global address pool that
contains the interface address pool segment and assigns them to the DHCP
clients.
A DHCP server assigns IP addresses in interface address pools or global address
pools to DHCP clients in the following sequence:
■
IP addresses that are statically bound to the MAC addresses of DHCP clients
■
IP addresses that are ever used by DHCP clients. That is, those in the assigned
leases recorded by the DHCP server. If there is no record in the leases and the
DHCP-DISCOVER packets sent by DHCP clients contain option 50 fields, the
DHCP server assigns the IP address requested by option 50.
■
The first IP address found among the available IP addresses in the DHCP
address pool.
■
If no IP address is available, the DHCP server queries lease-expired and
conflicted IP addresses. If the DHCP server finds such IP addresses, it assigns
them; otherwise the DHCP server does not assign IP addresses.
Global Address
Pool-Based DHCP
Server Configuration
Configuration Tasks
Table 461 Global address pool-based DHCP server configuration tasks
Configuration task Description Related section
Enable DHCP Required “Enabling DHCP”
on page 595
Configure global address pool mode on
interface(s) Optional “Configuring Global
Address Pool Mode
on Interface(s)” on
page 595