Which OSI layers does Ethernet operate at?
Ethernet operates in Layer 2 (Data Link) + Layer 1 (Physical).
What are the two sublayers of the Data Link Layer?
LLC and MAC
What is LLC responsible for
Identifies the network protocol within the frame
What is MAC responsible for?
Adds source/dest MAC addresses and controls access to the medium
What are the fields of an Ethernet frame?
Preamble | Destination MAC | Source MAC | EtherType | Data | FCS.
What are runt frames?
frames that are less than 64 bytes → discarded
What are giant frames?
Frames that are over 1518 bytes and are discarded
What is the minimum and maximum size of an Ethernet frame?
64 bytes (minimum), 1518 bytes (maximum)
How many bits in a MAC address, and how is it written?
48 bits (6 bytes), written in hexadecimal.
What do the first 3 bytes of a MAC address represent?
Vendor OUI (Organizationally Unique Identifier).
What are the three types of MAC addresses?
Unicast (one-to-one). Broadcast (FF-FF-FF-FF-FF-FF).
Multicast (e.g., IPv4 starts with 01-00-5E).
How does a switch learn MAC addresses?
From the source MAC of incoming frames → saves in MAC table.
What does a switch do if the destination MAC is unknown?
Floods the frame out all ports except incoming.
How long does a switch keep MAC table entries?
5 minutes (default)
What are the two main switching methods?
Store-and-Forward (checks FCS, safer, supports QoS). Cut-Through (low latency, forwards immediately).
What are the two types of Cut-Through switching?
Fast-forward (immediate, may pass errors).
Fragment-free (waits for 64 bytes, filters most collisions).
What is full-duplex vs half-duplex?
Full-duplex = both directions simultaneously.
Half-duplex = one direction at a time.
What is Auto-MDIX?
Feature that automatically detects and adjusts for crossover or straight-through cables.
