R3303-HP HSR6800 Routers Layer 3 - IP Services Configuration Guide
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Configuring the DHCP server
Overview
The DHCP server is well suited to networks where:
• Manual configuration and centralized management are difficult to implement.
• IP addresses are limited. For example, an ISP limits the number of concurrent online users, and most
users must acquire IP addresses dynamically.
• Most hosts do not need fixed IP addresses.
In addition to assigning IP addresses to DHCP clients on a public network, an MCE serving as the DHCP
server can also assign IP addresses to DHCP clients on private networks. Note that 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
DHCP address pools include common and extended address pools:
• Common address pool—Supports both static binding and dynamic allocation.
• Extended address pool—Supports only dynamic allocation.
Common address pool structure
The organization of the common address pool database can be compared to 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.
IP address lease durations are not inherited.
• Overridden if the lower level (child) has such configuration.
NOTE:
The extended address pools on a DHCP server are independent of each other and no inheritance
relationship exists among them.
Principles for selecting an address pool
The DHCP server observes the following principles to select an address pool when assigning an IP
address to a client: