Configuring Dhcp; Internal Dhcp Server; External Dhcp Servers; Dhcp Assignment - Cisco 2100 Series Configuration Manual

Configuring WLANs

Configuring DHCP

WLANs can be configured to use the same or different Dynamic Host Configuration Protocol (DHCP)
servers or no DHCP server. Two types of DHCP servers are available: internal and external.

Internal DHCP Server

The controllers contain an internal DHCP server. This server is typically used in branch offices that do
not already have a DHCP server. The wireless network generally contains 10 access points or fewer, with
the access points on the same IP subnet as the controller. The internal server provides DHCP addresses
to wireless clients, direct-connect access points, appliance-mode access points on the management
interface, and DHCP requests that are relayed from access points. Only lightweight access points are
supported. When you want to use the internal DHCP server, you must set the management interface IP
address of the controller as the DHCP server IP address.
DHCP option 43 is not supported on the internal server. Therefore, the access point must use an
alternative method to locate the management interface IP address of the controller, such as local subnet
broadcast, DNS, priming, or over-the-air discovery.
Refer to
Note
points find controllers:
http://www.cisco.com/en/US/products/ps6366/prod_technical_reference_list.html

External DHCP Servers

The operating system is designed to appear as a DHCP Relay to the network and as a DHCP server to
clients with industry-standard external DHCP servers that support DHCP Relay. This means that each
controller appears as a DHCP Relay agent to the DHCP server. This also means that the controller
appears as a DHCP server at the virtual IP Address to wireless clients.
Because the controller captures the client IP address obtained from a DHCP server, it maintains the same
IP address for that client during intra-controller, inter-controller, and inter-subnet client roaming.

DHCP Assignment

You can configure DHCP on a per-interface or per-WLAN basis. The preferred method is to use the
primary DHCP server address assigned to a particular interface.
Per-Interface Assignment
You can assign DHCP servers for individual interfaces. The management interface, AP-manager
interface, and dynamic interfaces can be configured for a primary and secondary DHCP server, and the
service-port interface can be configured to enable or disable DHCP servers.
Refer to
Note
Cisco Wireless LAN Controller Configuration Guide
6-8
Chapter 7 or the Controller Deployment Guide at this URL for more information on how access
Chapter 3 for information on configuring the controller's interfaces.
Chapter 6 Configuring WLANsWireless Device Access
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