📘 CCNA 200-301 v1.1
1.2 Describe Characteristics of Network Topology Architectures
1.2.d WAN (Wide Area Network)
1. What is a WAN?
A Wide Area Network (WAN) is a network that connects multiple Local Area Networks (LANs) over large geographical areas, such as between different cities, countries, or regions.
- LANs are usually within one location (like a single office building).
- A WAN connects these LANs together using service provider networks (like ISPs or telecom companies).
In other words, a WAN allows multiple branch offices, data centers, and remote users to communicate as if they were in the same network.
2. Why WANs are needed
Organizations use WANs when they have multiple sites.
For example:
- A company’s headquarters in one city and branch offices in other cities.
- Employees working remotely needing access to internal systems.
- Data centers connecting to cloud services.
Since these networks are far apart, they cannot be directly connected by Ethernet cables. So WANs use telecommunication networks and WAN technologies provided by service providers.
3. Key Characteristics of WANs
| Feature | Description |
|---|---|
| Large coverage area | Connects devices and LANs across cities, countries, or even continents. |
| Service Provider involvement | Uses telecom or ISP infrastructure to provide connectivity. |
| Slower speeds (compared to LANs) | Due to distance and shared provider infrastructure. |
| Higher cost | Because of leased circuits, dedicated lines, or service charges. |
| Different technologies | Uses technologies like MPLS, VPN, Metro Ethernet, Broadband, Cellular, etc. |
| Reliability and redundancy | WANs are designed for high uptime using redundant paths and failover systems. |
4. WAN Connection Types
There are two main categories of WAN connections:
a. Private WAN connections
These are dedicated and secure links managed by service providers.
Common types:
- Leased Line (Point-to-Point)
- A dedicated physical connection between two sites.
- Always active and offers constant bandwidth.
- Example: Connecting a headquarters directly to a branch router using a service provider’s fiber circuit.
- Protocols used: HDLC, PPP.
- MPLS (Multiprotocol Label Switching)
- A service provider WAN technology that directs packets using labels instead of IP routing.
- Offers quality of service (QoS) for prioritizing traffic (e.g., voice, video).
- Commonly used by enterprises for connecting multiple sites.
- Metro Ethernet
- Extends Ethernet technology across a city or metro area.
- Provides high-speed connectivity between offices in the same region.
- Easier to integrate with LANs since it uses Ethernet frames.
b. Public WAN connections
These use shared or public networks such as the Internet, with encryption to maintain security.
Common types:
- Broadband Internet (DSL, Cable, Fiber)
- High-speed Internet connections provided by ISPs.
- Used for smaller offices or as a backup WAN connection.
- VPN (Virtual Private Network)
- Creates a secure tunnel over the Internet between two sites.
- Uses encryption protocols like IPsec or SSL to keep data private.
- Cheaper than private WANs but relies on Internet quality.
- Cellular WAN (4G/5G)
- Uses mobile carrier networks for connectivity.
- Useful for remote or temporary locations where cables are not available.
5. WAN Devices
| Device | Purpose |
|---|---|
| Router | Connects LANs to WANs; determines best path for data to travel across networks. |
| CSU/DSU (Channel Service Unit / Data Service Unit) | Converts digital data from a router to a format suitable for WAN transmission (used with leased lines). |
| Modem (Modulator-Demodulator) | Converts digital signals to analog for transmission over phone or cable lines (used for broadband WANs). |
| Firewall | Provides security by filtering and inspecting WAN traffic. |
| VPN Gateway | Creates and manages VPN tunnels for encrypted communication over public WANs. |
6. WAN Topologies
WANs can connect multiple sites in different layouts depending on cost, reliability, and purpose:
| Topology | Description | Advantages | Disadvantages |
|---|---|---|---|
| Point-to-Point | Direct link between two sites. | Simple, reliable, fast. | Expensive for multiple sites. |
| Hub-and-Spoke | Central site (hub) connects to remote sites (spokes). | Easy to manage, cost-effective. | Traffic between spokes must go through the hub. |
| Full Mesh | Every site connects directly to every other site. | High reliability, low latency. | Very expensive and complex for many sites. |
| Partial Mesh | Some sites directly connected; others connect through intermediates. | Balance between cost and performance. | Less redundancy than full mesh. |
7. WAN Protocols and Encapsulation
When data travels from LAN to WAN, it needs to use a WAN protocol for transmission across service provider links.
Common WAN protocols:
| Protocol | Description |
|---|---|
| HDLC (High-Level Data Link Control) | Cisco default protocol for leased lines; supports error detection. |
| PPP (Point-to-Point Protocol) | More advanced than HDLC; supports authentication (PAP, CHAP). |
| Frame Relay (Legacy) | Packet-switching WAN technology; now mostly replaced by MPLS. |
| MPLS | Uses labels instead of IP headers for faster routing through the provider’s backbone. |
| Ethernet WAN (Metro Ethernet) | Uses Ethernet frames for WAN connections; very common in modern networks. |
8. WAN Security Considerations
Since WANs transmit data over large distances — often through public or provider networks — security is very important.
Key measures:
- Encryption: Protects data from being read by others (e.g., IPsec VPN).
- Authentication: Ensures devices are legitimate (e.g., PPP CHAP).
- Firewalls: Control traffic between LAN and WAN.
- Intrusion Prevention Systems (IPS): Detect and block suspicious WAN traffic.
9. WAN vs. LAN (Comparison)
| Feature | LAN | WAN |
|---|---|---|
| Coverage area | Small (office/building) | Large (cities, countries) |
| Ownership | Organization owns | Service provider owned |
| Speed | High (1 Gbps or more) | Lower (typically Mbps range) |
| Cost | Lower | Higher |
| Technology | Ethernet, Wi-Fi | MPLS, VPN, Broadband |
| Management | Managed internally | Managed by provider |
10. Summary for Exam Focus
For the CCNA 200-301 exam, you should understand:
✅ Definition and purpose of WAN
✅ WAN connection types (Private vs Public)
✅ Common WAN technologies: MPLS, Metro Ethernet, VPN, Broadband
✅ Basic WAN topologies: Point-to-Point, Hub-and-Spoke, Full Mesh
✅ WAN devices (Router, CSU/DSU, Modem, Firewall)
✅ WAN protocols (HDLC, PPP, MPLS)
✅ WAN security methods (Encryption, VPNs)
✅ Comparison of LAN vs WAN
