IP Routing

IP routing is the process of forwarding IP packets from a source device to a destination device across multiple networks. When a device receives an IP packet, it examines the destination IP address to determine whether the packet should be forwarded to another network or processed locally.

To route a packet to its destination, a device uses a routing table that maps network addresses to outgoing interfaces. The routing table is typically built dynamically through a routing protocol or manually configured by a network administrator.

When a device receives an IP packet, it first checks its own routing table to determine if it knows a route to the destination network. If a route is found, the packet is forwarded to the next hop router or the destination device. If a route is not found, the packet is either dropped or forwarded to a default gateway, which is a device that knows how to reach other networks.

Routing protocols are used to automatically share routing information between routers and build the routing table dynamically. Examples of routing protocols include Routing Information Protocol (RIP), Open Shortest Path First (OSPF), and Border Gateway Protocol (BGP). These protocols exchange information about network topology and path costs to determine the best path to a destination network.

IP routing is a critical component of the internet and large enterprise networks. It enables devices to communicate across multiple networks and provides fault tolerance by allowing traffic to be rerouted in case of network failures.