A network administrator is adding a new LAN to a branch office. The new LAN must support 61 connected devices. What is the smallest network mask that the network administrator can use for the new network?
- 255.255.255.240
- 255.255.255.224
- 255.255.255.192
- 255.255.255.128
Explanation: To support a LAN with 61 connected devices, the network administrator must select a subnet mask that provides a sufficient number of usable host addresses while minimizing wasted address space. The number of usable hosts is calculated using the formula 2n−2, where n represents the number of host bits remaining in the mask. A subnet mask of 255.255.255.192 (which corresponds to a /26 prefix) leaves 6 bits for the host portion, providing 62 usable host addresses. This is the most efficient (smallest) mask among the choices because the next tighter mask, 255.255.255.224 (/27), only provides 30 usable addresses, which is insufficient for the 61 required devices. While the 255.255.255.128 (/25) mask would also accommodate the devices, it provides 126 usable addresses and would therefore result in a significant number of unused IP addresses compared to the /26 option.
Related exam: CCNA 1 v7 Course Final Exam Answers
