What is IP Routing?

IP routing is that the method of sending packets from a host on one network to another host on another, remote network. This method is completed by routers. Routers examine the destination ip address of a packet , confirm the next-hop address, and forward the packet.

Routers use routing tables to determine a next hop address to which the packet should be forwarded.
Consider the subsequent example of ip routing:

Host A desires to speak with host B, however host B is on another network. Host A is designed to send all packets destined for remote networks to router R1. Router R1 receives the packets, examines the destination ip address and forwards the packet to the outgoing interface related to the destination network.

Default gateway
A default gateway could be a router that hosts use to speak with different hosts on remote networks. A default gateway is employed once a host doesn’t have a route entry for the specific remote network and doesn’t skills to succeed in that network. Hosts will be designed to send all packets destined to remote networks to a default gateway, that features a route to reach that network.

The following example explains the thought of a default gateway a lot of thoroughly.

Host A has an ip address of the router R1 configured because the default gateway address. Host A is making an attempt to speak with host B, a host on another, remote network. Host A appearance up in its routing table to see if there's an entry for that destination network. If the entry isn't found, the host sends all data to the router R1. Router R1 receives the packets and forwards them to host B.

Routing table
Each router maintains a routing table and stores it in RAM. A routing table is used by routers to determine a path to a destination network. every routing table consists of the following entries:

1. network destination and a network subnet mask – specifies a variety of ip addresses
2. remote router – ip address of the router wont to reach that network
3. outgoing interface – outgoing interface the packet should quit to reach the destination network

There are three completely different ways for populating a routing table:
• directly connected subnets
• using static routing
• using dynamic routing

Each of this methodology is described within the following chapters.

Consider the subsequent example. Host A desires to speak with host B, however host B is on another network. Host A is designed to send all packets destined for remote networks to the router. The router receives the packets, checks the routing table to see if it's an entry for the destination address. If it does, the router forwards the packet out the suitable interface port. If the router doesn’t find the entry, it discards the packet.