Networking & Cellular
MAC MAC Addresses — Study Guide
This guide covers MAC Addresses as part of Networking & Cellular. Start with the vocabulary, then try to answer each question before revealing the answer. Connect these facts to a real network or cellular connection and practice the subject in the arcade when you are ready.
Acronyms first
| Term | Meaning |
|---|---|
| MAC | Media Access Control |
Key facts
MAC addresses operate at which OSI layer?
Layer 2 — Data Link
Layer 2 manages error-free node-to-node transfer between two ____ nodes.
adjacent
Which three Layer 1 challenges does the Ethernet protocol solve at Layer 2?
Framing, Addressing, Error Detection
Order the Ethernet frame fields from first to last.
Preamble → SFD → Destination Address → Source Address → Type → Data → FCS
How long is the Ethernet Preamble?
7 bytes
How long is the Start of Frame Delimiter (SFD)?
1 byte
How long is each MAC address field (Dest./Source) in the frame?
6 bytes
How long is the Type field?
2 bytes
Ethernet data payload size range?
46–1500 bytes
How long is the Frame Check Sequence (FCS)?
4 bytes
Which field announces an incoming frame so receivers can synchronize, and is practically part of Layer 1?
Preamble
What bit sequence signals the end of the preamble (SFD)?
1010 1011
Which field determines the higher-level protocol in the payload (Ethernet II)?
Type
Payloads smaller than minimum get ____; larger ones can use ____.
padding; Jumbo Frames
The FCS uses which algorithm to detect corruption?
Cyclic Redundancy Check (CRC)
If sender and receiver CRC values don't match, the frame is…
discarded
CRC is based on binary division with a…
generating polynomial
A MAC address is how many bits?
48 bits
A MAC address is represented as…
12-digit hexadecimal
Hexadecimal is base ___ using 0–9 and A–F.
16
Convert binary 1010 to a single hex digit.
A
Convert binary 1111 to a single hex digit.
F
Convert binary 1100 to a single hex digit.
C
Convert binary 0111 to a single hex digit.
7
Convert binary 1011 to a single hex digit.
B
Convert binary 1101 to a single hex digit.
D
Which Windows command shows your NIC's physical (MAC) address?
ipconfig /all
Which hardware provides the MAC address for your device?
NIC (Network Interface Card)
NICs are implemented as expansion cards or…
direct motherboard integration
The first 3 bytes (6 hex digits) of a MAC are called the…
OUI (Organizationally Unique Identifier) / block ID
Who allocates OUIs to hardware makers?
IEEE
Matching a MAC address to its manufacturer via OUI is called…
Reverse (OUI) lookup
The second 3 bytes of a MAC are the…
Device ID (extension identifier)
The Device ID is sequentially assigned by the manufacturer based on…
date of issue
2^48 MAC addresses ≈ how many?
281 trillion
What are the 3 kinds of Ethernet addresses in LAN communications?
Unicast, Multicast, Broadcast
For a UNICAST MAC, the least significant bit of the first octet is…
0
For a MULTICAST MAC, the least significant bit of the first octet is…
1
Which address type sends from one source to ALL other LAN devices (e.g., ARP)?
Broadcast
Which address type sends from one source to SEVERAL specific devices?
Multicast
IP addresses operate at which OSI layer?
Layer 3 — Network
Which is the PHYSICAL identifier that theoretically never changes?
MAC address
Which is a LOGICAL identifier that can be dynamically assigned (e.g., by an ISP)?
IP address
IPv4 length?
32 bits (4 bytes)
IPv6 length?
128 bits (16 bytes)
Higher-layer encryption also encrypts MAC address data.
False
Kismet is an example of a…
wireless packet sniffing tool
Which is NOT listed as a challenge to MAC uniqueness?
CRC recalculation
MAC address spoofing causes disruption of communication and a…
false origin
Which iOS version introduced MAC randomization (as shown)?
iOS 8
Which named attack is an example of MAC ID used for nefarious purposes?
ShadowHammer
Which transit system implemented MAC address tracking in 2019?
London Underground (TfL)
Bypassing MAC filters, software licenses, and access to media are motives for…
MAC address spoofing
ARP identifies the ____ address affiliated with a given IP address, storing it in the ARP cache.
hardware (MAC)
An ARP request is a ____ and the reply is a ____.
broadcast; unicast
ARP spoofing/poisoning is what kind of attack?
Man-in-the-Middle
Per the check-on-learning, a hub works at which OSI layer?
1
Practice this module
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