Question

Describe the process that is used when a packet is received at a router. Describe processing and outcomes. Also, include the default information to make a working routing table.

Answer 1

Routing process inside a router is very interesting to know. Let us state, we need to surf the internet and we typed some web address in the browser to communicate with the web server.

A browser which is a user agent takes a shot at layer 7 i.e. application layer adds a header to the data and advances it to the transport layer. The transport layer adds another header to the packet which is called segment on the transport layer.

Then the data passes down to the network layer, which includes another header top of what it received from the transport layer and advances the packet to the data link layer. The network layer likewise includes the source IP address and the destination IP address in the packet.

Data link layer includes another header top of it and advances that to the physical layer. The packet at the data link layer is called frame.

For the Routing purpose, each router maintains a database table called the routing table. Each routing table will normally have the IP address of the network of the forwarding link. With the advancement in the routing algorithms, Routing tables otherwise called the Routing Information Base (RIB) started to have some metrics associated with those routes.

Only for the understanding purpose, a metric associated with the routes could be the distance (hops) to another node, link speed of the associated links or ISP rules, etc.

Routing Table is normally stored in the RAM of the router. It does not just have the information about the directly connected networks (via interfaces), yet additionally, it has information about the remote networks.

All IP-enabled devices, including routers and switches, use routing tables.

A routing table contains the information necessary to advance a packet along the best way toward its destination. Each packet contains information about its origin and destination. When a packet is received, a network device examines the packet and matches it to the routing table entry providing the best counterpart for its destination. The table then provides the device with instructions for sending the packet to the next bounce on its route over the network.