A MAC address is a physical address assigned to the network interface card (NIC) during manufacturing. It's a permanent, hardware-level identifier. It remains the same unless the NIC is physically changed.

An IP address (Internet Protocol address) is a logical address assigned to a device when it connects to a network. It's used for routing data packets across networks, including the internet. IP addresses can be static (manually assigned) or dynamic (assigned by a DHCP server).

Both MAC and IP addresses are necessary for a device to communicate on the internet because they serve different purposes:

• MAC Address: Used for communication within a local network (e.g., your home network). It ensures that data is delivered to the correct device on the same network segment.
• IP Address: Used for communication across networks, including the internet. It allows data packets to be routed from the source to the destination, even if they travel through multiple networks.

Without a MAC address, data wouldn't be delivered to the correct device on the local network. Without an IP address, data wouldn't be routed across the internet to the intended destination.

A router uses a routing table to determine the best path for a data packet to reach its destination. The routing table is a fundamental component of a router's operation.

The routing table contains entries that map destination networks (or individual hosts) to the next hop – the next router or network to which the packet should be sent. Each entry typically includes the destination network, the next hop IP address, and a 'metric' or cost associated with that path. The metric indicates the desirability of using that path; lower metrics are generally preferred.

When a data packet arrives at the router, the router examines the packet's destination IP address. It then searches its routing table for an entry that matches the destination network. If a match is found, the routing table entry specifies the next hop – the IP address of the next router or network to which the packet should be forwarded. The router then modifies the packet's header to reflect this next hop and forwards the packet accordingly. If no exact match is found, the router will use a best-match algorithm to select the most appropriate route based on the destination IP address.

An IP address (Internet Protocol address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. Its primary purpose is to uniquely identify a device, allowing data to be routed correctly across the network. Think of it like a postal address for a computer.

IPv4 is the older version, using a 32-bit address space. This results in approximately 4.3 billion unique addresses. IPv4 addresses are typically written in dotted decimal notation (e.g., 192.168.1.1). However, the IPv4 address space is now largely exhausted.

IPv6 is the newer version, using a 128-bit address space. This provides a vastly larger number of possible addresses (approximately 3.4 x 10³⁸). IPv6 addresses are written in hexadecimal notation, separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). IPv6 was developed to address the limitations of IPv4 and to support the growing number of internet-connected devices. Key advantages of IPv6 include simplified header structure, improved security features, and stateless address autoconfiguration.