Ethernet and Switching

CCNA1 Midterm Practice Exam

CSMA/CD

An access method rule for Ethernet.

CSMA/CA

Manages contention-based access on wireless networks.

CSMA/CD behavior

Devices listen before transmitting.

MAC address

Uniquely identifies Ethernet devices at the data link layer.

MAC sublayer functions

Adds headers/trailers and manages media access.

Data link layer service

Encapsulates Layer 3 packets into frames.

Half-duplex

Data flows in one direction at a time.

LLC sublayer

Communicates with network layer protocols.

Data link layer

Specifies media encapsulation methods.

NIC attribute (MAC address)

Places it at the data link layer.

IEEE

Defines data link layer standards.

Star topology

Created by connecting devices to a central switch.

CSMA/CD obsolescence

Due to full-duplex switches.

Auto-MDIX

Detects and adjusts for cable type.

Cut-through switching

Forwards frames quickly based on source MAC.

Switch actions

Builds MAC tables and forwards frames.

Auto-MDIX

Adjusts for straight-through or crossover cables.

Frame handling

Discards frames with non-matching MAC addresses.

Ethernet characteristic

Supported by IEEE 802.3 standards.

MAC address uniqueness

Must be globally unique (except virtual).

Switch

Forwards frames based on destination MAC.

MAC address structure

First 3 bytes are vendor OUI.

MAC table building

Records source MAC addresses.

Minimum Ethernet frame size

64 bytes.

Multicast MAC prefix

01-00-5E.

01-00-5E-0A-00-02

A multicast address.

Switch

Sends data based on MAC table entries.

Runt frames

Dropped by switches.

Multicast MAC prefix (IPv4),

First 24 bits: 01-00-5E