Aruba AP Discovery Process

 

Aruba AP Discovery Process

2011-06-13 17:32

一、Aruba ADP

Once the AP receives the IP address of the master controller, the AP uses this address as the IP address of a TFTP server and downloads its software image.  After the AP completes the download of its image, it repeats the boot-up process to obtain the same IP address of the master controller for bootstrapping/obtaining its configuration.
 
The ADP protocol is the first method that all Aruba APs will use to discover the master. The ADP protocol works as follows:
1  AP sends out a discovery packet
2  Master responds with its own loopback address – local controllers .may also respond with the loopback address of the master
3  AP connects to the correct controller and downloads its configuration as well as any new firmware
4  AP reboots and goes operational with correct configuration

 

1  Auto Discovery Protocol (ADP) – broadcast 

In the broadcast version of ADP, an Aruba AP sends out broadcast packets using the broadcast address 255.255.255.255.  The master or local controllers will then respond to the AP with the master loopback address.

Comment:

Important:  This method requires the master or other controllers to be located on the same Layer 2 network as the AP.

CLI：

(Aruba2400) (config) #adp discovery enable
(Aruba2400) (config) #adp igmp-join disable

2  Auto Discovery Protocol (ADP) -  multicast 

With the multicast version, an Aruba AP sends out IP multicast packets using the group address 224.0.82.11. The controllers will reply to the AP with its own loopback IP address.  

Comment:

This method requires the network to correctly pass multicast traffic between the AP and the controllers. 

CLI:

(Aruba2400) (config) #adp discovery enable
(Aruba2400) (config) #adp igmp-join enable

 

3  Dynamic Host Configuration Protocol (DHCP Option 43)

DHCP servers are a popular way of configuring clients with basic networking information such as an IP address, a default gateway,
network mask, DNS server, etc. Most DHCP servers have the ability to also send a variety of optional information as well. One of these is the Vendor-Specific Option Code, often called option 43. 
 
Here is how option 43 works:
 
1  The DHCP client on an Aruba AP adds an optional piece of information called the Vendor Class Identifier Code (Option 60) to
its DHCP request. The value of this code is ArubaAP
2  The DHCP server sees the vendor information and checks if it has option 43 configured, if it does, it will send the Vendor-Specific
Option Code (43) to the client. The value of this option is the loopback address of the Aruba master
3  The AP gets a response from the DHCP server and checks if option 43 was returned, if it was, the AP contacts the master using the
supplied IP address

 

4  Domain Name Services – DNS lookup
In most cases this is the most popular discovery method. It has the advantage of working very well across both Layer 2 and Layer 3
networks.  If an Aruba AP fails to receive the IP address of the master controller via DHCP or either ADP method, the AP will use the IP
address of the domain name server it received from DHCP to perform a DNS lookup.  

Comment:

This method requires a DNS host entry that corresponds to the name of the master. By default, APs look for the entry aruba-master.

 

二、AP Boot Sequence

Aruba AP Dynamic boot sequence

1 AP learns AP Name / AP Group from bootrom
2 AP sends out DHCP request for IP address
3 If DHCP response includes vendor option 43 (masterip), AP will use this for Master IP address
4 If no vendor option specified, AP sends “ADP” packet to Multicast group 239.0.82.11
5 If no response to Multicast ADP, AP sends “ADP” packet as L2/L3 broadcast (configure Master Aruba controller as a DHCP helper recipient)
6 If no response, AP sends DNS query to server given by DHCP for “aruba-master.domain.com” where “domain.com” is domain given by DHCP.  AP will use this for Master IP address

Once AP determines Master IP address, boot continues from Step 2 in Static config

 

AP Static boot sequence
1 AP loads variables from bootrom
2 AP sends message to Aruba controller with its AP Name / AP Group
3 If needed, AP sends an TFTP request to Aruba controller and downloads OS image (establish PAPI (UDP 8211 )连接到无线交换机) (control Protocol)
4 Based on the AP Name / AP Group, the current controller may take control of this AP or direct it to another controller
5 AP authenticates to controller and establishes GRE tunnel

 client 与 AP 通信，AP将数据通过 GRE tunnel   传送到无线控制器

三、configuration

 

adp discovery {disable|enable} igmp-join {disable|enable} igmp-vlan <vlan>

 

(host) #show adp config

ADP Configuration
-----------------
key        value
---        -----
discovery  enable
igmp-join  enable
igmp-vlan  0