Network Layer

What is an IP Address?

An IP address is a numeric label assigned to every device on a network so it can be uniquely identified and reached — IPv4 uses a 32-bit address written as fou…

What is Subnetting?

Subnetting is the practice of dividing a larger IP network into smaller, logically separated sub-networks (subnets) by borrowing bits from the host portion of…

What is NAT (Network Address Translation)?

NAT (Network Address Translation) is a technique that maps multiple private IP addresses on an internal network to one or a few public IP addresses, allowing m…

What is DHCP (Dynamic Host Configuration Protocol)?

DHCP (Dynamic Host Configuration Protocol) is a network protocol that automatically assigns IP addresses and other configuration details — like subnet mask, de…

Router vs Switch: What is the Difference?

A switch connects devices within a single local network and forwards frames between them using MAC addresses, while a router connects separate networks togethe…

IPv4 vs IPv6: What Are the Differences?

IPv4 uses 32-bit addresses giving about 4.3 billion possible addresses, while IPv6 uses 128-bit addresses giving a practically unlimited pool, and IPv6 also si…

What is the Network Layer (OSI Layer 3)?

The Network layer is OSI Layer 3 — it is responsible for logical addressing (IP addresses) and routing, deciding the best path to move a packet from a source h…

What is ICMP (Internet Control Message Protocol)?

ICMP (Internet Control Message Protocol) is a Network-layer protocol used by routers and hosts to send diagnostic and error-reporting messages — such as 'desti…

What is IGMP (Internet Group Management Protocol)?

IGMP (Internet Group Management Protocol) is a Network-layer protocol that hosts and neighboring routers use to establish and manage multicast group membership…

What is RIP (Routing Information Protocol)?

RIP (Routing Information Protocol) is one of the oldest distance-vector routing protocols, used by routers to share reachability information within an autonomo…

What is OSPF (Open Shortest Path First)?

OSPF is a link-state interior gateway routing protocol that lets routers within a single autonomous system share their local link information with every other…

What is GRE (Generic Routing Encapsulation)?

GRE (Generic Routing Encapsulation) is a tunneling protocol that wraps one network-layer packet inside another, letting two endpoints carry traffic — including…

What is IPsec and How Does It Secure IP Traffic?

IPsec (Internet Protocol Security) is a suite of protocols that authenticates and encrypts IP packets at the network layer, most commonly used to build VPN tun…

CIDR Notation Explained

CIDR (Classless Inter-Domain Routing) notation expresses an IP address’s network prefix length as a suffix like /24, meaning the first 24 bits identify the net…

Private vs Public IP Addresses

A public IP address is globally unique and directly routable across the internet, while a private IP address comes from reserved ranges (like 10.0.0.0/8 or 192…

What is a Loopback Address?

A loopback address is a reserved IP address that a device uses to send traffic to itself, letting software test its own network stack without touching any phys…

Broadcast vs Multicast vs Unicast

Unicast sends a packet from one sender to exactly one receiver, broadcast sends it from one sender to every device on the local network segment, and multicast…

What are the IPv6 Address Types?

IPv6 defines three fundamental address types by how many recipients a packet reaches — unicast (one specific interface), multicast (a group of interfaces that…

MAC Address vs IP Address

A MAC address is a fixed, hardware-burned Layer 2 identifier used to deliver frames within a local network segment, while an IP address is a logical, reassigna…

What is a Default Gateway?

A default gateway is the router a device sends traffic to whenever the destination address is not on its own local network, acting as the exit point that forwa…

Hub vs Switch vs Router: What Is the Difference?

A hub is a dumb Layer 1 device that repeats every incoming signal out of all its other ports, a switch is a smart Layer 2 device that reads MAC addresses to fo…

What is a Network Gateway?

A network gateway is the node — usually a router — that sits at the boundary of a local network and provides the exit point to a different network, most common…

What is MTU (Maximum Transmission Unit)?

MTU (Maximum Transmission Unit) is the largest size, in bytes, that a single packet can have on a given network link without needing to be split, commonly 1500…

What is IP Fragmentation in Networking?

IP fragmentation is the process of splitting an IP packet larger than a link’s MTU into multiple smaller fragments, each carrying enough header information for…