When you purchase a block of AT&T Static IP addresses, the installation technician will allocate three of the addresses to the following network functions - 1 address as the network base address; 1 address for your AT&T Gateway; and 1 address as your broadcast address. Therefore, the number of usable addresses is three less than the total number of addresses in your block. The current block sizes are:
| Total Block Size | Usable Addresses |
| 8 | 5 |
| 16 | 13 |
| 32 | 29 |
| 64 | 61 |
| 128 | 125 |