A2.3.4 How Static Routing and Dynamic Routing Move Data Across Local Area Networks (HL only) Notes

Static Routing: Manual Path Configuration

The Process of Static Routing

1. Manual Configuration: A network administrator manually enters routing information into each router. This includes:
   1. Destination network address
   2. Subnet mask
   3. Next hop address or exit interface
2. Routing Table: Each router maintains a routing table with:
   1. Statically configured routes
   2. Directly connected networks
3. Packet Forwarding:
   1. When a packet arrives, the router examines its destination IP address.
   2. It searches the routing table for a matching route.
   3. If found, the packet is forwarded to the specified next hop or exit interface.
   4. If no match is found, the packet is dropped or sent to a default route if configured.

Advantages of Static Routing

1. Predictability: Routes are predefined, making network behavior more predictable.
2. Resource Efficiency: No additional processing power or bandwidth is needed for route updates.
3. Security: By controlling valid routes, administrators can enhance network security.

Disadvantages of Static Routing

1. Manual Maintenance: Requires manual updates for any network changes, which can be time-consuming.
2. Lack of Adaptability: Does not adapt to network changes, such as link failures, leading to potential downtime.
3. Scalability Issues: Becomes complex and error-prone in larger networks.

Dynamic Routing: Automated Path Discovery

The Process of Dynamic Routing

1. Routing Protocols: Routers use protocols like RIP, OSPF, or BGP to communicate and exchange routing information.
2. Route Discovery: Routers automatically discover network destinations and maintain up-to-date routing tables.
3. Path Selection: Routing protocols use algorithms to determine the best path based on metrics like:
   1. Hop count
   2. Bandwidth
   3. Latency
4. Adaptability: When network changes occur (e.g., link failures), the protocol recalculates paths and updates routing tables.

Advantages of Dynamic Routing

1. Adaptability: Automatically adjusts to network changes, reducing downtime.
2. Scalability: Efficiently manages large networks with minimal manual intervention.
3. Optimized Performance: Selects the most efficient routes based on real-time metrics.

Disadvantages of Dynamic Routing

1. Complexity: Initial configuration and maintenance can be more complex than static routing.
2. Resource Usage: Requires more processing power and bandwidth for route discovery and maintenance.
3. Convergence Time: The time it takes for routers to update their routing tables can affect network performance.

Comparing Static and Dynamic Routing

Factors to Consider When Choosing Routing Methods

1. Configuration:
   1. Static Routing: Requires manual setup, suitable for stable networks.
   2. Dynamic Routing: Automates configuration, ideal for dynamic environments.
2. Maintenance:
   1. Static Routing: High manual effort for updates.
   2. Dynamic Routing: Minimal manual intervention, adapts to changes.
3. Complexity:
   1. Static Routing: Simple for small networks, complex for large ones.
   2. Dynamic Routing: Initially complex but manages large networks efficiently.
4. Resource Usage:
   1. Static Routing: Minimal resource consumption.
   2. Dynamic Routing: Higher resource demands for route discovery and maintenance.
5. Convergence:
   1. Static Routing: No convergence, as routes are fixed.
   2. Dynamic Routing: Convergence time varies, affecting network performance.
6. Scalability:
   1. Static Routing: Poor scalability in large networks.
   2. Dynamic Routing: Scales well with network size and complexity.
7. Network Size:
   1. Static Routing: Best for small to medium-sized networks.
   2. Dynamic Routing: Suited for medium to large networks with frequent changes.