Subnetting

Summary

This video tutorial focuses on IP version 4 subnetting. It explains how to divide a network into subnets, detailing how subnetting reduces the number of hosts in each network while increasing the number of network IDs. The tutorial covers key concepts such as network and broadcast addresses, subnet mask calculations, and subnetting for Class A, B, and C IP addresses. It includes practical steps using Cisco Packet Tracer to simulate and test different subnet configurations, demonstrating how packets are routed between PCs, switches, and routers while emphasizing the importance of gateways for communication across networks.

Takeaways

• 😀 Subnetting in IPv4 is the process of dividing a network into multiple smaller sub-networks.
• 🔑 Subnetting is typically performed on IP addresses from Class A, B, and C.
• 🌐 Subnetting increases the number of network IDs but reduces the number of hosts per network.
• 📉 In every subnet or network, two special IP addresses are reserved: one for the network identifier and one for the broadcast.
• 🔢 A simple way to calculate subnetting is by using a subnet mask, which can divide a network into multiple subnets by changing the block sizes.
• ⚙️ When subnetting a Class C network (/24), it can be divided into smaller blocks, such as /25, /26, etc., reducing available IP addresses per block.
• 🚦 The subnet mask defines how many IP addresses are available within each subnet, which reduces as more bits are used for subnetting.
• 🌍 Gateways are essential for routing packets between different subnets, as they handle communication between devices not in the same subnet.
• 📡 Packet communication between subnets requires proper routing via gateways, and without a gateway, communication may fail.
• 💻 In Cisco Packet Tracer, a simulation demonstrates subnetting, routing, and communication behavior, including when devices without a gateway cannot communicate across subnets.

Q & A

What is the primary objective of this practicum?

The main objective is to understand subnetting concepts, the function of gateways, and to simulate network scenarios using Cisco Packet Tracer.

What is subnetting in IP addressing?

Subnetting is the process of dividing a large network into smaller sub-networks (subnets). This is typically done with IP address classes A, B, and C. Subnetting reduces the number of hosts in each network but increases the number of networks.

What happens to the host ID when subnetting is applied?

In subnetting, part of the host ID is sacrificed to create additional network IDs, resulting in a new, smaller set of host IDs for each subnet.

What are the two special IP addresses in a subnet?

The two special IP addresses in a subnet are the Network address, which identifies the subnet, and the Broadcast address, which is used to communicate with all devices in the subnet.

How is a Class C network typically subnetted?

In a Class C network, subnetting can divide the network into smaller blocks. For example, subnetting with a /25 prefix will create two subnets, each with 128 IP addresses. Subnetting further, such as with /26 or /27, creates more subnets but reduces the number of IP addresses in each subnet.

What is the formula used to calculate the subnet mask?

The subnet mask is calculated by subtracting the block size from 256. For example, for a /25 subnet, the block size is 128, so the subnet mask is 255.255.255.128.

What is the impact of not assigning a gateway to certain PCs in the scenario?

If a PC does not have a gateway assigned, it will be unable to communicate with devices outside of its own subnet. This is because the gateway is responsible for routing traffic between different subnets.

How does communication between PCs in different subnets work in this scenario?

Communication between PCs in different subnets involves sending the packet to a router via the gateway. The router forwards the packet to the appropriate subnet, allowing communication between devices on different networks.

Why is the communication between some PCs incomplete in the simulation?

Communication is incomplete for PCs that lack a gateway. Without a gateway, these PCs cannot route traffic to devices in other subnets, causing the communication to fail.

What is the role of simulation mode in Cisco Packet Tracer during this practicum?

The simulation mode in Cisco Packet Tracer allows users to observe the path of packets as they move through the network, helping them understand how packets are routed between devices and subnets.