What is a Routing Table?
A database used by routers to determine the best path for forwarding packets to their destination.
Key Components of a Routing Table:
1. Destination: The IP address of the destination network.
2. Next Hop: The IP address of the next router to send the packet.
3. Metric: A value used to choose the best path (e.g., hop count, bandwidth).
4. Interface: The router’s outgoing interface to reach the next hop.
Types of Routing Entries:
1. Directly Connected: Routes to networks directly attached to the router.
2. Static Routes: Manually configured routes.
3. Dynamic Routes: Automatically learned via routing protocols (e.g., RIP, OSPF, BGP).
Routing Table Lookup Process:
1. Check for exact match (longest prefix match).
2. Select the route with the lowest metric.
3. Forward to the next hop or interface.

Type: Greedy algorithm.
Purpose: Finds the shortest path from the source to all other nodes.
Steps:
1. Start from the source node.
2. Assign a cost of 0 to the source and infinity to all other nodes.
3. Visit the node with the smallest cost and update neighbors’ costs.
4. Repeat until all nodes are visited.
Key Feature: Builds a shortest-path tree (SPT).
Best for: Networks with reliable links.

Type: Distance-vector algorithm.
Purpose: Calculates the shortest path from a single source to all other nodes.
Steps:
1. Start with all distances set to infinity, except the source (0).
2. Relax all edges repeatedly (update costs if a shorter path is found).
3. Repeat for (n-1) iterations, where n = number of nodes.
Key Feature: Handles negative weights.
Best for: Smaller networks or dynamic topologies.

Routing Table: “Destination Next, Metric Best!” (Destination, Next Hop, Metric).
Dijkstra: “DJ = Direct Journey!” (Shortest path).
Bellman-Ford: “BF = Best Friend for all paths!”

Concepts of Routing Tables and Shortest Path Algorithms