Explain the concept of routing tables and how they are used in routing decisions.

Routing tables are data structures used by routers to determine the best path for forwarding network traffic. They contain a list of network destinations and the corresponding next-hop addresses or interfaces to reach those destinations.

When a router receives a packet, it examines the destination IP address and consults its routing table to determine the appropriate next-hop for forwarding the packet. The routing table is populated through various methods such as static routing, dynamic routing protocols, or default routes.

Each entry in the routing table typically includes the destination network address, subnet mask, next-hop address, and metric. The destination network address represents the network or subnet to which the packet needs to be forwarded. The subnet mask helps in determining the network portion of the destination IP address.

The next-hop address or interface specifies where the packet should be sent next. It can be a specific IP address of the next router or the interface connected to the destination network. If the next-hop address is not known, the router may drop the packet or forward it to a default route.

The metric is a value assigned to each entry in the routing table, indicating the cost or preference of a particular route. It helps the router in selecting the best path among multiple available routes to the same destination. The metric can be based on factors like bandwidth, delay, reliability, or administrative distance.

Routing tables are dynamic and can change based on network topology changes or updates received from neighboring routers. Routing protocols like OSPF, EIGRP, or BGP exchange routing information to update the routing tables. This allows routers to adapt to network changes and make optimal routing decisions.

In summary, routing tables are crucial components of routers that store information about network destinations and help in making routing decisions by determining the best path for forwarding network traffic. They enable efficient and reliable communication within a network by ensuring packets are delivered to their intended destinations.