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