1.2 Describe characteristics of network topology architectures
📘CCNA 200-301 v1.1
✅ STAR, MESH, BUS, RING — CCNA Explanation
Network topologies describe how devices (nodes) are connected in a network. While modern networks mostly use star and partial mesh, CCNA still expects you to understand all four classic topologies.
⭐ 1. Star Topology
Star topology is the most common in modern Ethernet LANs.
How it works
All devices connect to a central device:
- Switch (modern networks)
- Hub (legacy)
Characteristics
- Centralized connection point
- Easy to add/remove devices
- Failure of a single device → no effect on the rest.
- Failure of the central switch → entire network down
Advantages
- Easy to manage and troubleshoot
- High performance (each device gets dedicated bandwidth with switches)
- Scalable
Disadvantages
- Dependent on the central device
- Requires more cabling than bus/ring
Where used
- Ethernet LANs
- Office networks
- Home networks
🔗 2. Mesh Topology
Used in environments where high availability and redundancy are required.
Types
- Full Mesh: Every device connects to every other device
- Partial Mesh: Only critical devices are interconnected
Characteristics
- High redundancy
- Multiple paths → better fault tolerance
- Complex cabling and configuration
Advantages
- Very reliable
- Supports load balancing
- Failure of one link does NOT disrupt the network
Disadvantages
- Expensive (more cabling & ports)
- Harder to manage
- Not suitable for large environments
Where used
- WANs
- Data centers
- Service providers
- SD-WAN topologies (partial mesh)
🚌 3. Bus Topology
A very old topology, rarely used today but still exam-relevant.
How it works
All devices share a single backbone cable (coaxial in older networks).
Characteristics
- Uses a single shared medium
- Requires terminators at both ends
- Collisions were common (legacy Ethernet / CSMA/CD)
Advantages
- Simple and inexpensive
- Requires less cabling
Disadvantages
- If the backbone fails → entire network down
- Collisions reduce performance
- Troubleshooting is difficult
- Limited cable length
Where used
- Legacy Ethernet (10BASE2, 10BASE5)
- Temporary small networks
🔁 4. Ring Topology
Devices connect in a circular path.
How it works
Each device connects to two others:
- One upstream
- One downstream
Data travels in one direction (or both directions in dual-ring).
Characteristics
- Failure in one node may break the loop
(unless it’s a dual ring) - Uses token passing in Token Ring networks
Advantages
- Predictable performance (no collisions)
- Good for structured traffic flow
Disadvantages
- A single fault can disrupt entire network (unless dual-ring)
- Slow and outdated compared to modern Ethernet
Where used
- Legacy IBM Token Ring
- SONET / SDH (fiber WAN technologies use a version of ring)
📘 CCNA Key Comparison Table
| Topology | Modern Use? | Redundancy | Cost | Performance | Failure Impact |
|---|---|---|---|---|---|
| Star | ✔ Widely used | Medium | Medium | High | Central device failure → full outage |
| Mesh (full/partial) | ✔ WAN, DC | High | High | High | Very resilient |
| Bus | ❌ Outdated | Low | Low | Low | Backbone failure → full outage |
| Ring | Rare | Medium | Medium | Predictable | Node/link failure breaks the ring (single-ring) |
