Network Addressing (Full Explanation)
Layer 3 network addressing is a key responsibility of the Network Layer. Network Addresses are inherently logical, meaning they are software-based and can be modified through appropriate configurations.
A network address consistently directs to a host, node, or server, and it can also signify an entire network. This address is typically set on the network interface card and is usually associated with the MAC address (the hardware address or layer-2 address) of the device for Layer-2 communication.
Various types of network addresses exist:
- IP
- IPX
- AppleTalk
IP addressing offers a way to distinguish between hosts and networks. Since IP addresses are allocated hierarchically, each host is always part of a specific network. For a host to communicate beyond its subnet, it must know the destination network address to which the packet or data is directed.
Hosts located in different subnets require a method to find each other. This function is fulfilled by DNS, a server that provides the Layer-3 address of a remote host linked to its domain name or FQDN. Once a host obtains the Layer-3 Address (IP Address) of the remote host, it sends all its packets to its gateway. A gateway is a router that possesses all the necessary information to route packets to the intended host.
Routers utilize routing tables, which contain the following details:
- Method to reach the network
When routers receive a forwarding request, they send the packet to the next hop (the adjacent router) on the way to the destination.
The subsequent router in the sequence follows the same procedure, and ultimately, the data packet arrives at its destination.
A network address can fall into one of these categories:
- Unicast (intended for a single host)
- Multicast (intended for a group)
- Broadcast (intended for all)
- Anycast (intended for the nearest one)
By default, a router does not forward broadcast traffic. Multicast traffic, which typically consists of high-priority video or audio streams, receives special handling. Anycast operates similarly to unicast, but in this case, packets are sent to the closest destination when several options are present.
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