Users Guide

523| Access Points Dell Networking W-Series ArubaOS 6.5.x| User Guide
l Controller addresses derived from the server-name and server-ip provisioning parameters and the
default controller name aruba-master are added to the list. Note that if a DNS name resolves to multiple
addresses, all addresses are added to the list.
Controller Discovery using DNS
When using DNS, AP learns multiple IP addresses to associate with a controller. If the primary controller is
unavailable or does not respond, the AP continues through the list of learned IP addresses until it establishes a
connection with an available controller. This takes approximately 3.5 minutes per controller.
It is recommended you use a DNS server to provide APs with the IP address of the master controller because it
involves minimal changes to the network and provides the greatest flexibility in the placement of APs.
APs are factory-configured to use the host name aruba-master for the master controller. For the DNS server
to resolve this host name to the IP address of the master controller, you must configure an entry on the DNS
server for the name aruba-master.
Controller Discovery using ADP
ADP is enabled by default on all Dell APs and controllers. With ADP, APs send out periodic multicast and
broadcast queries to locate the master controller. ADP requires that all APs and controllers are connected to
the same Layer-2 network. If the devices are on different networks, you must use a Layer-3 compatible
discovery mechanism, such as DNS, DHCP, or IGMP forwarding.
To use ADP discovery:
1. Issue the command show adp config to verify that ADP and IGMP join options are enabled on the
controller, If ADP is not enabled, you can reenable ADP using the command adp discovery enable and
adp igmp-join enable.
2. If the APs are not in the same broadcast domain as the master controller, you enable multicast on the
network (ADP multicast queries are sent to the IP multicast group address 239.0.82.11) for the controller
to respond to the APs’ queries. You also must make sure that all routers are configured to listen for Internet
Group Management Protocol (IGMP) join requests from the controller and can route these multicast
packets. C
Controller discovery using a DHCP Server
You can configure a DHCP server to provide the master controller’s IP address. You must configure the DHCP
server to send the controller’s IP address using the DHCP vendor-specific attribute option 43. The APs identify
themselves with a vendor class identifier set to DellAP in their DHCP requests. When the DHCP server
responds to a request, it will send the controller’s IP address as the value of option 43.
When using DHCP option 43, the AP accepts only one IP address. If the IP address of the controller provided
by DHCP is not available, the AP can use the other IP addresses provisioned or learned by DNS to establish a
connection. For more information on how to configure vendor-specific information on a DHCP server, see
DHCP with Vendor-Specific Options on page 1101 or refer to the documentation included with your server.
Enable DHCP to Provide APs with IP Addresses
Each AP requires a unique IP address on a subnetwork that has connectivity to a controller. It is recommended
you use the Dynamic Host Configuration Protocol (DHCP) to provide IP addresses for APs; the DHCP server
can be an existing network server or an controller configured as a DHCP server.
If you do not enable DHCP, each AP must be manually configured with an IP address through the AP provisioning
profile. For details, see .