M9: IPv4 & Network Segmentation

Module 9 CISCO Networking, IPv4 and Segmentation

Unicast

A single source device sends a packet to a single destination device. It is one‑to‑one communication.

Broadcast

Is one‑to‑all communication. One device sends a message, and every device in the same network must process it.

Broadcast Domain

it includes all hosts on the same Layer 2 network segment. All devices connected to the same switch (or group of switches) belongs here.

Layer 2

The layer in OSI model that is responsible for local network communication. Communication handled using MAC addresses, not IP routing. Traffic forwarded by switches, not routers.

Multicast

One‑to‑many (selected group) communication.
A host sends one packet, and only subscribed devices receive it.
This reduces unnecessary traffic compared to broadcast.

Public IPv4 Address

Globally unique. Routable on the internet. Assigned by ISPs. Used for devices that must be reachable from outside the network.

Private IPv4 Address

Not routable on the internet. Used inside homes, offices, and organizations. Can be reused by anyone (not globally unique). Created to slow IPv4 exhaustion.

IPv6

It was created to permanently solve IPv4 address exhaustion.

Network Address Translation

It converts private IP → public IP so the packet can travel across the internet. The translation happens in the router.

Loopback Address

Used by a device to send traffic to itself (self‑test). Ping this IP to check own device’s IP configuration. Special and limited communication rules. Range: 127.0.0.1

Link-Local Address

Used when a device cannot get an IP address from DHCP or other methods. Think = “I gave myself an IP because DHCP didn’t answer.” Special and limited communication rules.

Classful addressing

Networks were divided into Classes A, B, and C, each with fixed sizes. It is used until the mid 1990s.

Classless Addressing

• Introduced to stop waste and allocate addresses efficiently.

• Ignores class boundaries.

• Networks are assigned based on actual need, not fixed classes.

• This is the system used today.

Internet Assigned Numbers Authority

The organization who manages IP Addresses. Top level authority for IPv4 and IPv6. Manages the global IP pool. Allocates large address blocks to RIR.

Regional Internet Registries

The regional organizations responsible for IPs allocation for a specific region.

Address Resolution Protocol

A network function that finds the MAC address for a known IPv4 address.

Dynamic Host Configuration Protocol

A network function that finds a specific server to get an IP configuration.

Network Segmentation

is the practice of dividing a large network into smaller, separate sections. Physical

Subnetting

It is used to fixed the problem of large broadcast domains. The large network is divided into smaller broadcast domains. Logical

Directed Broadcast

is a message sent to all hosts on a specific network. It is useful for sending a broadcast to all hosts on a nonlocal network.

Limited Broadcast

is used for a communication that is limited to the hosts on the local network.