NetworkingNetwork+

Ethernet Standards for CompTIA Network+ N10-009

Ethernet is the dominant Layer 2 LAN technology, governed by the IEEE 802.3 standard. CompTIA Network+ N10-009 tests Ethernet standards by speed, media type, and naming conventions. You must recognize standard names (like 1000BASE-T or 10GBASE-SR), decode their meaning, and match them to correct media and distances. Ethernet also appears in questions about half-duplex vs full-duplex, CSMA/CD, and MAC addressing.

8 min

3 sections · 7 exam key points

2 practice questions

Ethernet Naming Convention

IEEE Ethernet standards follow a naming pattern: [Speed][BASE or BROAD]-[Media type]. The speed is in Mbps or Gbps. BASE means baseband (single channel using full bandwidth); BROAD means broadband (rarely used now). The media designator indicates cable type: T = twisted pair copper, F = fiber, S = short wavelength fiber, L = long wavelength fiber, X = Ethernet-specific encoding.

Examples decoded: 10BASE-T = 10 Mbps, baseband, twisted pair. 100BASE-TX = 100 Mbps (Fast Ethernet), twisted pair. 1000BASE-T = 1 Gbps (Gigabit Ethernet), twisted pair, requires Cat5e+. 10GBASE-T = 10 Gbps, twisted pair (Cat6a/Cat7). 10GBASE-SR = 10 Gbps, short-range fiber. 10GBASE-LR = 10 Gbps, long-range fiber. 40GBASE-SR4 = 40 Gbps, short-range fiber (4 lanes).

Common Ethernet Standards and Their Media

10BASE-T (10 Mbps): Cat3 minimum, 100m, obsolete. 100BASE-TX (Fast Ethernet, 100 Mbps): Cat5 minimum, 100m — still used in some environments. 1000BASE-T (Gigabit Ethernet, 1 Gbps): Cat5e minimum, 100m — the standard for most modern LANs. 1000BASE-SX: 1 Gbps, multimode fiber, up to 550m (OM3). 1000BASE-LX: 1 Gbps, single-mode or multimode fiber, 5km SMF.

10GBASE-T: 10 Gbps, Cat6a (100m) or Cat6 (55m) — brings 10GbE to copper. 10GBASE-SR: 10 Gbps, multimode fiber, 300m (OM3) — common in data centers. 10GBASE-LR: 10 Gbps, single-mode fiber, 10km. 25GBASE-T: 25 Gbps, Cat8 (30m). 40GBASE-SR4: 40 Gbps, MMF using 4 parallel lanes, 150m. 100GBASE-SR4: 100 Gbps, 4-lane MMF, 100m.

CSMA/CD, Duplex, and MAC Addresses

CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is the original Ethernet access control method. Devices listen before transmitting; if a collision occurs, they back off for a random period and retransmit. CSMA/CD is only relevant in half-duplex environments (hubs). Full-duplex switched networks eliminate collisions — CSMA/CD is inactive.

Half-duplex: a device can send or receive but not simultaneously (walkie-talkie model). Full-duplex: simultaneous send and receive — requires a point-to-point switched connection. All modern switched ports default to full-duplex. Speed and duplex mismatches cause performance problems — a port set to auto-negotiate on one end and hard-coded on the other can result in a duplex mismatch.

MAC addresses are 48-bit (6-byte) hardware addresses expressed in hex (e.g., 00:1A:2B:3C:4D:5E). The first 3 bytes are the OUI (Organizationally Unique Identifier) — identifies the manufacturer. The last 3 bytes are assigned by the manufacturer. Broadcast MAC address = FF:FF:FF:FF:FF:FF. Multicast MACs start with 01:00:5E.

Key Ethernet Standards Quick Reference

Standard	Speed	Media	Max Distance
100BASE-TX	100 Mbps	Cat5 UTP	100 m
1000BASE-T	1 Gbps	Cat5e UTP	100 m
1000BASE-SX	1 Gbps	Multimode fiber	550 m
1000BASE-LX	1 Gbps	SMF/MMF	5 km (SMF)
10GBASE-T	10 Gbps	Cat6a UTP	100 m
10GBASE-SR	10 Gbps	Multimode fiber	300 m
10GBASE-LR	10 Gbps	Single-mode fiber	10 km

Key exam facts — Network+

1000BASE-T: Gigabit Ethernet over Cat5e, 100m — the most common LAN standard
10GBASE-SR: 10G over multimode fiber, short range (300m on OM3)
10GBASE-LR: 10G over single-mode fiber, long range (10km)
CSMA/CD applies only to half-duplex (hub-connected) environments
Full-duplex eliminates collisions — used in all modern switched networks
MAC address: 48 bits; first 3 bytes = OUI (manufacturer); FF:FF:FF:FF:FF:FF = broadcast
Speed/duplex mismatch = common cause of poor network performance

Common exam traps

CSMA/CD is used by modern switched Ethernet

CSMA/CD is only active in half-duplex environments. Modern full-duplex switched ports do not use CSMA/CD because simultaneous send and receive eliminates collisions

1000BASE-T requires Cat6 cable

1000BASE-T requires Cat5e minimum — Cat5e's improved crosstalk performance was specifically designed to support Gigabit Ethernet

MAC addresses are assigned by software and can be changed

MAC addresses are hardware addresses burned into the NIC by the manufacturer (OUI-based). They can be spoofed in software, but the underlying hardware address is fixed

Practice questions — Ethernet Standards

These questions are representative of what you will see on Network+ exams. The correct answer and explanation are shown immediately below each question.

Q1.A network engineer selects 10GBASE-LR for a fiber link between two buildings 8 kilometers apart. Which type of fiber is required?

A.OM1 multimode

B.OM3 multimode

C.Single-mode fiber

D.Cat6a copper

Explanation: 10GBASE-LR (Long Range) uses single-mode fiber (SMF) and supports distances up to 10 kilometers. Multimode fiber (OM1, OM3) is used with short-range standards like 10GBASE-SR and cannot reach 8 km. Cat6a is copper and limited to 100 meters.

Q2.A workstation connected to a switch experiences slow performance and high error rates. Which issue is most likely the cause?

A.MAC address conflict

B.Duplex mismatch

C.Incorrect subnet mask

D.Excessive VLANs

Explanation: A duplex mismatch occurs when one side negotiates full-duplex and the other is set to half-duplex. The half-duplex side uses CSMA/CD and detects collisions when the full-duplex side transmits simultaneously, causing errors, retransmissions, and poor performance. This is a classic troubleshooting scenario on the Network+ exam.

Frequently asked questions — Ethernet Standards

What does 'BASE' mean in Ethernet standard names?

'BASE' stands for baseband, meaning the cable carries a single channel that uses the full available bandwidth. This contrasts with 'BROAD' (broadband), which divides the cable into multiple channels using frequency multiplexing. Virtually all modern Ethernet uses baseband signaling.

What is the difference between 1000BASE-SX and 1000BASE-LX?

1000BASE-SX uses short-wavelength (850nm) lasers designed for multimode fiber — maximum distance is 550m on OM3. 1000BASE-LX uses long-wavelength (1310nm) lasers and supports both single-mode (5km) and multimode (550m with mode conditioning patch cord) fiber. Use LX for longer campus runs; SX for short data center interconnects.

Practice this topic

Network+practice questions

Test yourself on Ethernet Standards

JT Exams routes you to questions in your exact weak areas — automatically, after every session.

Free practice test Start 7-Day Free Trial

No credit card · Cancel anytime