If you read the API-README and can access the full config file of the miner, you can turn on mcast so the API of every miner, with mcast enabled, will respond to a single mcast message on the network ...

The miner.php can also use that so that the php finds all your miners, with mcast enabled, without you having to tell it their IPs

https://github.com/kanoi/cgminer/blob/master/API-README