Routing is one of the most important concepts in computer networking. Whenever data needs to travel from one network to another, routing decides the best path for that data. From accessing websites to connecting cloud services, routing works silently in the background to ensure smooth communication.
This blog explains routing in networking, how routing works, and the types of routing protocols including static routing, dynamic routing, RIP, OSPF, and BGP, in a simple and interview-friendly way.
What Is Routing in Networking?
Routing is the process of selecting the best path for data packets to travel from a source network to a destination network. This task is performed by devices called routers.
Routers use routing tables and routing protocols to decide where to forward packets next so that they reach the correct destination efficiently.
Why Routing Is Important
Routing plays a critical role in network communication.
It helps to:
- Connect multiple networks
- Enable communication across LAN, WAN, and MAN
- Choose the most efficient path for data
- Handle network failures and congestion
- Support scalability and reliability
Without routing, communication would be limited to only local networks.
How Routing Works
Routing works using routing tables stored inside routers.
A routing table typically contains:
- Destination network
- Subnet mask
- Next hop address
- Exit interface
- Metric or cost
When a router receives a packet, it checks the destination IP address and selects the best matching route from the routing table.
Types of Routing
Routing can be broadly classified based on how routes are created and maintained.
Static Routing
Static routing is a method where routes are manually configured by a network administrator. Routers do not automatically learn or update routes.
Characteristics of Static Routing
- Routes are manually added
- No automatic updates
- Simple and predictable
- No routing protocol required
Advantages
- Low overhead
- High security
- Full control over routing paths
Disadvantages
- Not scalable
- Requires manual updates
- Not suitable for large or frequently changing networks
Static routing is commonly used in small networks or for default routes.
Dynamic Routing
Dynamic routing uses routing protocols to automatically learn, update, and maintain routes.
Routers exchange routing information with each other and adapt to network changes such as link failures or topology updates.
Advantages
- Scales well
- Automatically adapts to network changes
- Reduces manual configuration
Disadvantages
- Uses more CPU and bandwidth
- More complex than static routing
Dynamic routing is widely used in enterprise and service provider networks.
Types of Dynamic Routing Protocols
Dynamic routing protocols are classified based on how they calculate routes.
Distance Vector Routing Protocols
Distance vector protocols calculate the best path based on distance (hop count) and direction. Routers share routing information periodically with neighbors.
RIP (Routing Information Protocol)
RIP is one of the oldest dynamic routing protocols.
Key features:
- Uses hop count as a metric
- Maximum hop count is 15
- Simple to configure
- Slow convergence
RIP is suitable only for very small networks.
Link State Routing Protocols
Link state protocols build a complete map of the network topology and calculate the shortest path.
OSPF (Open Shortest Path First)
OSPF is one of the most widely used interior routing protocols.
Key features:
- Uses cost as a metric
- Fast convergence
- Supports large networks
- Uses areas for scalability
OSPF is commonly used in enterprise networks.
Path Vector Routing Protocols
Path vector protocols maintain the entire path information to reach a destination network.
BGP (Border Gateway Protocol)
BGP is used to route traffic between different autonomous systems.
Key features:
- Used on the internet backbone
- Uses path attributes instead of hop count
- Highly scalable
- Policy-based routing
BGP is critical for large-scale and cloud networks.
Interior vs Exterior Routing Protocols
Routing protocols are also classified based on where they are used.
Interior Gateway Protocols (IGP)
Used within a single organization or autonomous system.
Examples:
- RIP
- OSPF
Exterior Gateway Protocols (EGP)
Used between different organizations or autonomous systems.
Example:
- BGP
Routing Metrics Explained
Routing metrics are values used by routing protocols to determine the best path.
Common routing metrics include:
- Hop count
- Cost
- Bandwidth
- Delay
- Reliability
Different protocols use different metrics to calculate optimal routes.
Routing vs Switching
Routing and switching serve different purposes:
- Switching operates at Layer 2 and forwards frames within a network
- Routing operates at Layer 3 and forwards packets between networks
Both are essential for complete network communication.
Routing in Real-World Networks
Routing is used in many real-world scenarios such as:
- Internet communication
- Enterprise WAN connectivity
- Cloud networking and VPC routing
- Firewall and VPN routing
- Load balancing and high availability
Routing ensures data reaches the correct destination securely and efficiently.
Common Routing Interview Questions
Interviewers often test routing fundamentals.
Common questions include:
- Difference between static and dynamic routing
- How does OSPF work?
- Difference between RIP, OSPF, and BGP
- What is an autonomous system?
- What metrics are used in routing protocols?
Strong conceptual understanding matters more than memorizing commands.
Conclusion
Routing is a foundational networking concept that enables communication between networks. By understanding how routing works and learning the differences between static routing, dynamic routing, and routing protocols like RIP, OSPF, and BGP, networking professionals can design scalable, reliable, and efficient networks. Routing knowledge is essential for enterprise networking, cloud infrastructure, and network engineer interviews.
