HBA provides a basic load balancing concept according to RFC3074. HBA stands for hash bucket allocation and defines whether the DHCP Server is responsible for a client or not. The HBA consists of 32 hex values separated by a single blank. Every hex number represents eight bits, one bit per hash bucket. The DHCP server calculates a hash value for every client that asks for an IP address. The hash value is between 0 and 255. If the correspondig HBA bit for that hash value is 1, then the client is serviced. If it is 0 then the client is not serviced. Please assume the following example:
[Settings] HBA=FF FF FF FF FF FF 00 00 FF FF FF FF FF FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
This restricts the DHCP Server to service clients whose hash value is 0 through 47 or 64 through 127. The server servicing the rest of the clients should have the exact opposite HBA. The HBA logic kicks in only for clients that are unknown (not yet in the INI file) to the DHCP Server. Clients who are already known are serviced regardless of the HBA.