option space CiscoAP;
option CiscoAP.server-address code 241 = array of ip-address;
set vendor-string = option vendor-class-identifier;

class "cisco-aps" {
       match if substring (option vendor-class-identifier, 0, 8) = "Cisco AP";
       vendor-option-space CiscoAP;
       option CiscoAP.server-address 151.216.253.21;
}