1. What is Routing?
✔ Routing is the process of finding the best path for data packets to travel across networks.
✔ Routers use a routing table to decide where to send packets.
Types of Routing
Routing can be of two types:
- Static Routing
- Dynamic Routing
2. Static Routing
Definition
Static routing means routes are manually added to a router by a network administrator.
Key Characteristics
- Manual Configuration
Every route must be added and changed manually. - No Overhead
Does not use CPU, memory, or bandwidth to learn routes. - Fixed Paths
The path remains the same unless someone manually changes it. - Best for Small Networks
Works well when the network is simple and does not change often.
Advantages of Static Routing
- Very easy to configure in small networks.
- No extra CPU or bandwidth required.
- Gives full control to administrators.
- More secure, since no routing packets are exchanged.
Disadvantages of Static Routing
- Becomes difficult to manage in large networks.
- Not scalable for networks that change frequently.
- No automatic failover – if a link fails, routes must be changed manually.
- Time-consuming for large organizations.
Static Route Example
In Cisco routers:
ip route <destination> <subnet mask> <next-hop>
Example:
Router A (192.168.1.0/24) wants to reach Router B (192.168.2.0/24)
ip route 192.168.2.0 255.255.255.0 10.0.0.2
This sends all traffic for 192.168.2.0/24 via 10.0.0.2.
3. Dynamic Routing
Definition
Dynamic routing means routers automatically learn and update routes using routing protocols.
Key Characteristics
- Automatic Updates
Routers adjust to network changes in real time. - Uses Routing Protocols
Examples: RIP, OSPF, EIGRP, BGP - Consumes System Resources
Uses CPU, memory, and bandwidth to exchange routing information. - Best for Large Networks
Useful in large, complex, and changing networks.
Advantages of Dynamic Routing
- Automatically updates routes when the network changes.
- Reduces manual work for administrators.
- Handles large networks easily.
- Supports automatic failover during link failures.
Disadvantages of Dynamic Routing
- Requires more CPU, memory, and bandwidth.
- Needs proper configuration.
- May take some time to converge (update routes) after a network change.
Types of Dynamic Routing Protocols
| Protocol Type | Examples | Description |
|---|---|---|
| Distance Vector | RIP | Uses hop count, simple but slow |
| Link-State | OSPF | Faster, more efficient, uses full topology |
| Hybrid | EIGRP | Mix of distance vector + link state (Cisco only) |
| Path Vector | BGP | Used between ISPs (Internet backbone protocol) |
4. Static vs Dynamic Routing
| Feature | Static Routing | Dynamic Routing |
|---|---|---|
| Configuration | Manual | Automatic |
| Scalability | Low (small networks) | High (large networks) |
| Adaptability | Does not adapt | Automatically adjusts |
| Resource Usage | No CPU/memory use | Uses CPU, memory, bandwidth |
| Failure Recovery | Manual | Automatic failover |
| Ease of Use | Easy for small networks | Easy for large networks |
| Protocols Required | None | Yes (RIP, OSPF, etc.) |
5. Routing Table
Definition
A Routing Table is a list stored inside routers that shows:
- Destination networks
- Next hop address
- Interface to send packets
- Metric (cost)
Static Routes
Added manually by administrator.
Dynamic Routes
Added automatically by routing protocols.
6. Simple Example to Understand Routing
Situation:
Two networks want to communicate:
- Network A: 192.168.1.0/24
- Network B: 192.168.2.0/24
Routers must know how to reach each other.
Static Routing Example
Router A:
ip route 192.168.2.0 255.255.255.0 10.0.0.2
Router B:
ip route 192.168.1.0 255.255.255.0 10.0.0.1
7. Dynamic Routing Protocols Overview
RIP
- Uses hop count
- Max hops = 15
- Good for very small networks
OSPF
- Link-state protocol
- Fast convergence
- Used in medium and large organizations
EIGRP
- Hybrid protocol
- Fast and intelligent
- Cisco proprietary
BGP
- Path-vector protocol
- Used on the Internet
- Connects ISPs globally
- Handles huge routing tables
8. Easy Mnemonics to Remember
Static Routing
“Set in Stone” → fixed → no automatic changes.
Dynamic Routing
“Dynamic Dance” → always moving → updates automatically.
9. Exam Focus Points
These points are frequently asked in banking and IT exams:
- Difference between static and dynamic routing
- Which routing method is used in large networks? (Dynamic)
- Which routing method needs manual configuration? (Static)
- Which protocols are dynamic routing? (RIP/OSPF/BGP/EIGRP)
- Which routing method gives automatic failover? (Dynamic routing)
- Advantages/disadvantages of both routing types
- Understand the command to add static routes
10. Quick Summary
Static Routing
- Manual
- Simple but not scalable
- No automatic updates
- Best for small networks
- No CPU/bandwidth usage
Dynamic Routing
- Automatic
- Scalable
- Adapts to changes
- Requires routing protocols
- Best for medium and large networks
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