Technical data

Option 43

The active slave is now in control. If the first active slave Ethernet interface goes

down, the slave controller fails over to the second Ethernet interface.

To revert the failover, verify that the first interface on the Slave controller is up and

running. Then, bring up the first interface of the original Master controller. The N+1

active slave becomes a passive slave and the original N+1 master becomes the N+1

Master again.

Option 43

Option 43 is not part of any Meru product; it is a method for mapping controllers.

With DHCP Option 43, you can specify a primary and backup controller for APs. With

this configuration, the backup controller can be in a different subnet from the

primary controller. Option 43 implements redundancy by specifying which controllers

(primary and secondary) an AP should associate to. This feature is supported across

all access points. A backup controller can be configured using either DHCP or DNS.

For example, using Option 43, if “wlan-controller” is mapped to P1 (and P1 has a

redirect to P2) and “wlan-controller-2” is mapped to S1 (and S1 has a redirect to S2),

the discovery order would be P1, P2, S1, S2. If a controller has both a DNS entry and

Option 43 enabled, the AP will first use the host address as configured on the AP

(default value = wlan-controller). If the host address is configured as 0.0.0.0 or if the

host is a name and the name cannot be resolved using DNS, only then will the AP look

at the DHCP Option 43 value.

For specific Option 43 configuration directions, see the Support Portal How-To

4062-125.

AP Aware Redundancy using DHCP Option 43

 Configure APs with L3 preferred and the controller name as 0.0.0.0

 On the DHCP server, Option 43 values need to be configured with primary and

secondary controller IPs and/or hostnames. Then, when an AP contacts the DHCP

server to obtain an IP address, it also receives primary and secondary controller

IP information using the Option 43 value from the DHCP server.

Caution!

If the first interface on the Slave controller is not running when the Master

controller’s first interface is brought online, the Active Slave would transition to a Passive

Slave. However, since the first interface is not online, the N+1 module will assume that the

Master controlelr is down and try to resume the Master role itself. This can cause a loop in

functionality. To avoid this, always ensure that the first interface on the Slave controller is

up prior to bringing up the same interface on the Master controller.