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CCNA 7 ITN- Introduction to Networks- Module 11 IPv4 Addressing -Subnetting part 5

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Summary

This video, part of the CCNA Module 11, continues the subnetting topic, specifically focusing on IPv4 addressing. It provides a detailed walkthrough of how to subnet a network into smaller segments for different host requirements, including calculations for subnets, block sizes, and valid host addresses.

Highlights

Subnetting for Network B (20 Hosts)

00:00:26

The video revisits the network topology, identifying Network B which requires 20 hosts. To accommodate this, a /27 subnet is chosen from the available /26 slice. The calculation involves subtracting the old slash (26) from the new (27), resulting in 2 subnets. The block size for this /27 subnet is determined to be 32 (256 - 224).

Calculating Network B Addresses

00:02:06

The two subnets generated from the previous calculation are 192.160.10.192/27 and 192.160.10.224/27. The first valid host for the 192.160.10.192/27 subnet is 192.160.10.193, and the last valid host is 192.160.10.222. The broadcast address is 192.160.10.223. This subnet is assigned to Network B.

Subnetting for Links (Slash 30)

00:04:23

For interconnecting networks (links), the video emphasizes using a /30 subnet mask as it is the most efficient and prevents IP address wastage. Breaking up the previous /27 subnet for a link, the calculation (30 - 27) yields 8 subnets. The block size for /30 is 4 (256 - 252).

Configuring Link Addresses

00:05:30

The generated /30 subnets start from 192.160.10.224. One of these subnets, 192.160.10.224/30, is used for the link between Network A and Network B. Its first valid IP is 192.160.10.225, and the last is 192.160.10.226, with a broadcast of 192.160.10.227.

Assigning IP Addresses and Default Gateways

00:07:27

The video demonstrates how to assign IP addresses and default gateways. For LAN A, the default gateway is 192.160.10.190/26, and client PCs would receive addresses like 192.160.10.129, 192.160.10.130, up to 192.160.10.189. For the link, addresses like 192.160.10.225 and 192.160.10.226 would be used.

Subnetting with /24 and Smaller

00:09:39

The video then addresses subnetting for networks requiring more than 256 hosts, using an example of 500 hosts. A /23 subnet is needed for 500 hosts. The calculation (23 - 22) yields 2 subnets. A new rule for block size is introduced: if the last byte of the mask is zero, subtract from the third byte (256 - 254), resulting in a block size of 2.

Calculating Addresses for Large Subnets

00:11:15

The two subnets derived from the /23 calculation are 12.83.160.0/23 and 12.83.162.0/23. The first valid host for the 12.83.160.0/23 subnet is 12.83.160.1, and the last valid host is 12.83.161.254, with a broadcast of 12.83.161.255. This is assigned to LAN A.

Subnetting for Network B (100 Hosts) with a Larger Network

00:13:08

For Network B, requiring 100 hosts within the larger network, a /25 subnet is chosen. Calculating from the /23, (25 - 23) results in 4 subnets. The block size for /25 is 128 (256 - 128). The subnets generated are 12.83.162.0/25, 12.83.162.128/25, 12.83.163.0/25, and 12.83.163.128/25.

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