問68
頻出度★★★
MACアドレスに関する記述のうち, 適切なものはどれか。
平成28年度 春期 ITパスポート試験 問68
テクノロジ系ネットワーク › ネットワーク方式
This question's explanation and your answers so far.
解説
問 68
- ア
正解 A MAC address is a 48-bit identifier burned into the hardware of a network interface (NIC), such as a LAN card, during manufacturing. The upper 24 bits are the OUI that the IEEE assigns to each manufacturer (vendor), and the lower 24 bits are assigned by each vendor to its own products so that they never overlap. Through this two-level management, addresses are assigned uniquely so that no two devices in the world have the same address. Therefore, choice ア, which states that “it is assigned so that only one device in the world has the same address,” is correct.
Incorrectイ
The upper bits of a MAC address form the OUI that identifies the manufacturer; they do not contain country information. Moreover, the assignment is designed to be unique across the entire world, not “one per country,” so this choice is wrong on two counts.
Incorrectウ
A MAC address is fixed and assigned to the device at manufacturing time; it is not assigned by a network administrator. What an administrator assigns per device is the IP address (static assignment or DHCP configuration), which operates at a different layer than the MAC address.
Incorrectエ
What a provider (ISP) assigns to a user is a global IP address and the like, not a MAC address. ISPs are not involved with MAC addresses; these are assigned in advance by the device's manufacturer.
ここがポイント
- A MAC address is a 48-bit physical address that the manufacturer burns into the device's NIC; because the IEEE manages the upper 24-bit OUI, it is assigned to be unique (non-duplicated) worldwide.
- Distinction from the IP address: an IP address is a logical address assigned by an administrator, DHCP, or an ISP, whereas a MAC address is a physical address fixed at manufacturing time and contains no country information.
用語