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

option 43 will return the Aruba master IP address to an Aruba DHCP client. This information allows Aruba APs to auto-discover their master and gain their configuration.