🔌💡 Ethernet Standards and Connectivity
Deep dive into Ethernet types, speeds, transceivers, and real-world troubleshooting scenarios.
⚡ Ethernet Standards and Real-World Connectivity
Ethernet is the foundation of modern LAN networking. Below is a breakdown of standards, duplex modes, transceivers, and common connectivity issues.
📡 100BaseT Standards
100BaseT refers to Fast Ethernet, offering speeds up to 100 Mbps over twisted pair copper cables.
| Standard | Cable Type | Max Length | Duplex Support |
|---|---|---|---|
| 100Base-TX | Cat 5/5e UTP | 100 m | Half/Full Duplex ✅ |
| 100Base-FX | Multi-mode fiber | 2 km | Full Duplex ✅ |
| 100Base-T4 | Cat 3 (Obsolete) | 100 m | Half Duplex ❌ Full |
- Full Duplex: Data is sent and received simultaneously (no collisions 🚀).
- Half Duplex: One direction at a time, uses CSMA/CD (collision detection).
🚀 Gigabit and 10-Gigabit Ethernet
✅ Gigabit Ethernet (1000 Mbps)
| Standard | Medium | Max Distance |
|---|---|---|
| 1000Base-T | Cat 5e/6 (UTP) | 100 m |
| 1000Base-SX | Multi-mode fiber | 220–550 m |
| 1000Base-LX | Single-mode fiber | 5 km |
| 1000Base-CX | Shielded copper | 25 m |
💡 All 4 twisted pairs are used in 1000Base-T, unlike 100Base-TX.
🧠 SONET Support
SONET (Synchronous Optical Network) uses:
- 1000Base-LX10 for long distance over fiber (up to 10 km)
- Used in metro and backbone connections
🔥 10-Gigabit Ethernet (10 Gbps)
| Standard | Medium | Max Distance | Notes |
|---|---|---|---|
| 10GBase-T | Cat 6a/Cat 7 | 100 m | Cost-effective, copper |
| 10GBase-SR | Multi-mode fiber | 26–400 m | Short reach |
| 10GBase-LR | Single-mode fiber | 10 km | Long reach |
| 10GBase-ER | Single-mode fiber | 40 km | Extended reach |
| 10GBase-CX4 | Twinax copper cable | 15 m | Early short-distance option |
| 10GBase-LRM | Multi-mode fiber | 220 m | Legacy support |
| 10GBase-ZR | Single-mode fiber | 80 km | Vendor-specific standard |
🔌 Ethernet Transceivers
Transceivers convert electrical signals to optical or vice versa. They are modular, hot-swappable, and standardized.
🔎 Common Transceivers
| Type | Description |
|---|---|
| GBIC (Gigabit Interface Converter) | Older, large form factor |
| SFP (Small Form-factor Pluggable) | Gigabit-capable, common |
| SFP+ | Supports 10G Ethernet |
| QSFP | Quad SFP – 40G/100G capability |
🧠 MSA (Multi-Source Agreement): Ensures compatibility between vendors for form factors and connectors.
🧪 Real-World Ethernet Scenarios & Issues
🔁 Loop Issues (Without STP)
Two switches connected with two cables will form a loop. Without STP (Spanning Tree Protocol), this causes:
- Broadcast storms 📢🌪️
- MAC address table corruption
- Complete network meltdown 😱
✅ STP to the Rescue
STP disables one redundant link to prevent loops and re-enables it if the main link fails.
🌊 Flood Guard
A switch feature to detect and block MAC flooding attacks (DoS type).
🧯 Common Ethernet Problems
| Problem | Cause | Fix |
|---|---|---|
| Speed mismatch | One device on 100 Mbps, another on 1 Gbps | Auto-negotiation or manually set both to match |
| Duplex mismatch | One side Full, other Half – leads to collisions | Configure both sides the same |
| Switch mismatch | STP settings differ or VLAN tagging differs | Use consistent config and STP protocol (RSTP) |
| Bad uplink | Improper cable or port for uplink connection | Use uplink ports or crossover cable if needed |
| Cable faults | Damaged or incorrect cables (Cat 5 for 10G, etc.) | Replace or upgrade cables |
🛠️ Quick Reference: When to Use What?
| Speed | Medium | Scenario |
|---|---|---|
| 100 Mbps | Cat 5 | Old office networks, VoIP |
| 1 Gbps | Cat 5e/6 | Modern desktops, basic servers |
| 10 Gbps | Cat 6a/Fiber | Data centers, backbone links |
| 40–100 Gbps | QSFP | High-performance computing |
✅ Summary
- Understand the difference between copper vs. fiber, duplex modes, and transceiver types
- Match your devices' speed, duplex, and cabling
- Watch for loops, mismatches, and cable quality
🚦 Ethernet is simple, but errors in duplex/speed config or STP can cripple a network!