H3C Technologies H3C S12500 Series Switches - Manual (Page 48)

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Configuring the DHCP server
The DHCP server configuration is supported only on Layer 3 Ethernet interfaces (or subinterfaces), VLAN
interfaces, Layer 3 aggregate interfaces, and loopback interfaces. The subaddress pool configuration is
not supported on loopback interfaces.
Overview
Application environment
The DHCP server is well suited to the networks where:
• Manual configuration and centralized management are difficult to implement.
• Many hosts need to acquire IP addresses dynamically. This might be because the number of hosts
exceeds the number of assignable IP addresses, so it is impossible to assign a fixed IP address to
each host. For example, an ISP has a limited number of host addresses.
• A few hosts need fixed IP addresses.
In addition to assigning IP addresses to DHCP clients on public networks, a multi-VPN-instance customer
edge (MCE) switch serving as the DHCP server can also assign IP addresses to DHCP clients on private
networks. The IP address ranges of public and private networks or those of private networks on the DHCP
server cannot overlap each other. For more information about MCE, see MPLS Configuration Guide.
DHCP address pool
Address pool types
DHCP address pools include the following types:
• Common address pool—Supports both static binding and dynamic allocation.
• Extended address pool—Supports only dynamic allocation.
Common address pool structure
The common address pool database is organized as a tree. The root of the tree is the address pool for
natural networks, branches are address pools for subnets, and leaves are addresses statically bound to
clients. For the same level address pools, a previously configured pool has a higher selection priority than
a new one.
At the very beginning, subnets inherit network parameters and clients inherit subnet parameters.
Therefore, common parameters, for example a DNS server address, should be configured at the highest
(network or subnet) level of the tree.
The new configuration at the higher level (parent) of the tree is:
• Inherited if the lower level (child) has no such configuration.
• Overridden if the lower level (child) has such configuration.