External Dhcp Servers - Cisco SD2008T-NA Configuration Manual

Configuring WLANs
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.
Note Refer to
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.
Per-WLAN Assignment
WLANs that support management over wireless must allow management (device-servicing) clients to
obtain an IP address from a DHCP server. See the
page 5-6
Per-Interface Assignment
You can assign DHCP servers for individual interfaces. The Layer 2 management interface, Layer 3
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
Security Considerations
For enhanced security, Cisco recommends that operators require all clients to obtain their IP addresses
from a DHCP server. To enforce this requirement, all WLANs can be configured with a DHCP Required
setting and a valid DHCP server IP address, which disallows client static IP addresses. If DHCP
Required is selected, clients must obtain an IP address via DHCP. Any client with a static IP address is
not be allowed on the network. The controller monitors DHCP traffic because it acts as a DHCP proxy
for the clients.
If slightly less security is tolerable, operators can create WLANs with DHCP Required disabled and a
valid DHCP server IP address. Clients then have the option of using a static IP address or obtaining an
IP address from the designated DHCP server.
Operators are also allowed to create separate WLANs with DHCP Required disabled and a DHCP server
IP address of 0.0.0.0. These WLANs drop all DHCP requests and force clients to use a static IP address.
Note that these WLANs do not support management over wireless connections.
This section provides both GUI and CLI instructions for configuring your WLAN to use a DHCP server.
Cisco Wireless LAN Controller Configuration Guide
6-4
Chapter 7 or the Controller Deployment Guide at this URL for more information on how access
for instructions on configuring management over wireless.
Chapter 3 for information on configuring the controller's interfaces.
Chapter 6 Configuring WLANsWireless Device Access
"Using Management over Wireless" section on
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