Configuring the dhcp server, Introduction, Dhcp fundamentals – RuggedCom RuggedRouter RX1100 User Manual
Page 243: Dhcp network organizations, Dhcp client options
27. Configuring The DHCP server
Revision 1.14.3
243
RX1000/RX1100™
27. Configuring The DHCP server
27.1. Introduction
This chapter familiarizes the user with:
• DHCP Server Configuration
• Use of Option 82
27.1.1. DHCP Fundamentals
Dynamic Host Configuration Protocol (DHCP) is a method for centrally and consistently managing IP
addresses and settings for clients, offering a variety of assignment methods. IP addresses can be
assigned based on the Ethernet MAC address of a client, sequentially, or by using port identification
provided by a DHCP relay agent device.
27.1.1.1. DHCP Network Organizations
The information to assign addresses in DHCP is organized to deal with clients at the host, group,
subnet, pool and shared network level.
Hosts entries assign specific settings to a client based on its Ethernet MAC address.
Groups allow identical settings to be created for a group of hosts, making it simpler to manage
changes to the settings for all the hosts contained within the group. Groups contain hosts.
Pools contain ranges of IP addresses to hand out to clients with access rules to determine which
clients should receive addresses from that pool.
Subnets control settings for each subnet that DHCP serves. A subnet can include a range of IP
address to hand out to clients. Only one subnet can contain dynamic IP address ranges without any
access restrictions on any given physical port since DHCP doesn't know which subnet a client should
belong to when the request is received. Subnets contain groups, pools and hosts.
Shared networks are used when multiple subnets should be served by a single physical port. This
applies both when using a DHCP relay agent connected to the port with additional subnets behind
the relay agent, or when multiple virtual networks exist on one physical interface. Each subnet then
gets its own subnet definition inside the shared network rather than at the top level. Shared networks
contain subnets, groups and hosts.
27.1.1.2. DHCP Client Options
The following options apply to single hosts, subnets of hosts, pools (potentially discontinuous ranges
of addresses), shared networks (a single physical networks for which distinct subnets of hosts coexist
and request addresses) and groups. The meaning of each option is the same in each case, while the
type of target determines which clients it applies to.
In DHCP, settings at a more specific level overrides higher levels. For example you can configure a
DNS server for all clients, the create a group that overrides the setting. This allows defaults to be set
at a high level to apply to most clients, while exceptions can be places just where they are needed.