Configuring Microsoft DHCP server for the WLAN

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INTRODUCTION
NETGEAR ProSAFE WC9500 High Capacity Wireless Controllers support a wide range of wireless standards. In addition,
several vendor-specifi c DHCP options can either be implemented automatically or they can be specifi cally assigned to
NETGEAR ProSAFE access points managed by the WC9500 via the DHCP server. Standard DHCP options can be supplied
to provide the access points with specifi c network related information while NETGEAR vendor-specifi c options can be sup-
plied to facilitate discovery by the ProSAFE wireless controller.
OVERVIEW
Standard and vendor-specifi c DHCP options are provided to NETGEAR access points with the DHCP O er and DHCP ACK
forwarded from the DHCP server:
1. The NETGEAR ProSAFE access points broadcast a DHCP Discover message onto the physical network to discover
available DHCP servers. The DHCP server can be located either on the same IP subnet as the access point, or through
a Layer 3 enabled device that supports DHCP forwarding. The Layer 3 devices can forward DHCP packets to a DHCP
server on a di erent IP subnet. The DHCP Discover message will include DHCP option 55 (Parameter Request List)
which tells the DHCP server what DHCP options the NETGEAR access points wish to receive from the DHCP scope.
2. When a DHCP server receives a DHCP Discover message from an access point, it reserves an IP address and forwards
a lease by sending a DHCP O er message to the requesting access point. The DHCP O er will include the IP address
to be assigned, as well as any standard and vendor-specifi c DHCP options that are supported by the device and are
assigned to the DHCP scope.
3. A NETGEAR access point may receive DHCP O ers from multiple DHCP servers, but will only accept one of them. Once
it has accepted a DHCP O er, the access point will forward a broadcast DHCP Request message with a transaction ID
to inform the available DHCP servers which lease it has accepted. Each DHCP server with a lease that was not accept-
ed will return the o ered address to its pool of available addresses.
4. When the DHCP server receives the DHCP Request message from the access point, the DHCP process enters its fi nal
phase. The DHCP server serving the lease will forward a DHCP ACK message to the access point that includes the