Point DHCP clients to failover servers

[Roberto Carna]

Hi people, I've just implemented two ISC DHCP servers in failover configuration.

All my current DHCP clients point to Server A (primary), and now I
have also Server B (secondary).

All my DHCP clients come from a Wireless LAN Controller that points to
Server A in order to get IP addresses.

How do I have to add Server B (failover) in the Wireless Lan
Controller ??? Do I have to define any sentence in order to tell
priorities (first check Server A, after that check Server B) ???

My question in general is about failover definition in clients.

Thanks a lot, regards!!!

ROBERT