Contents

- News & Tools
- Assignment #2 Debriefing
- Subnetting Tutorial & Reference Page
- Subnetting Tips/Notes
- Subnetting into a Large Number of Subnets
- Determine the network address of a high subnet number.
- Converting a Decimal Number to Base 256 (Dotted-decimal)
- Do
- Do
- Better Focus and Efficient Studying When Not Multitasking

## News & Tools

**How To END The Climate Crisis In One Generation**| Paul Hawken on The Rich Roll Podcast- Regeneration.org: The world’s largest, most complete listing and network of solutions to the climate crisis. And how to do them!

- AnsibleFest 2021: Automate. Innovate. Accelerate. September 29–30, 2021

**Studying: what students do vs. what works (and why)****How to study effectively**by Paul Penn- Forget cramming, ditch the highlighter, and stop passively rereading.
- The psychology of learning offers better tactics.

- Memory is fundamentally reconstructive, as opposed to reproductive.

- When studying, it’s not what you think you know that matters, but rather what you can prove you know.
- The benefits of retrieval practice are not simply limited to facts; they also extend to concepts and the transfer of knowledge from one domain to another.

- Unpatched MacOS vulnerability lets remote attackers execute code
- Apple has deprecated the insecure Transport Layer Security (TLS) 1.0 and 1.1 protocols in recently launched iOS and macOS versions and plans to remove support in future releases altogether.
- Second farming cooperative shut down by ransomware this week

## Assignment #2 Debriefing

## Subnetting Tutorial & Reference Page

## Subnetting Tips/Notes

**If no mask/prefix is given, then borrow bits starting from the “Class” boundary of the IP address.****If a mask/prefix is given, then the given mask/prefix is the result of subnetting. (Borrow bits from the “Class” boundary to the given mask/prefix.)**

- The total number of subnets must be a power of 2.
- The total number of hosts must be a power of 2.
- Is the question asking for “
**subnets**” or “**hosts”**- If you’re asked for the # of hosts, then you must determine how many bits are needed to get that # of hosts, then subtract those bits from the 32 IPv4 bits, to determine the network bits / mask / prefix.

- Determine the
**number of subnets**: 2^{[number of bits borrowed]}. - Determine the
**total number of addresses**: 2^{ [the number of host bits]}. - Add the
**Wildcard mask**to the network/subnet address to determine the broadcast/last address in the network/subnet. - Block Size:
- The block size (
**256**– [**The interesting octet**]) is best used to determine the increment of the subnets. - The interesting octet is the last octet, from the left, that you borrowed bits from.
- The “block size” is the increment from one subnet to the next, within the “interesting” octet.
- The “block size” is not the number of addresses per subnet.

- The block size (
- Determine how many addresses to add to the network address/subnet zero to get to the target subnet.
- 1. Multiplying (Subnet “Number”) by the (number of addresses per subnet).

(For the Nsubnet, subtract 1 before multiplying by the number of addresses per subnet.)^{st, nd, rd, th} - 2. Convert the result to its Base-256 equivalent
- 3. Add the Base-256 equivalent to the original network address of the block to get the network/subnet address of the target subnet.

- 1. Multiplying (Subnet “Number”) by the (number of addresses per subnet).
- The “subnet address” is an alternate term for the “network address” of a subnet.
- Subnet using the methods that work for all subnets, large or small. Switching methods depending on the size of the subnet requires more effort than is necessary.
- Practice makes improvement!

## Subnetting into a Large Number of Subnets

- Incrementing subnets using the Block Size works for a small number of subnets, but is not efficient when you need hundreds or thousands or millions of subnets. It doesn’t scale.
- Using the Base-256 conversion method scales up.

## Determine the network address of a high subnet number.

- Multiply the target subnet number by the number of addresses per subnet, to get the number of addresses to add to the network address (subnet zero), to jump to the target subnet.
- Convert the resulting number of addresses to its Base-256 (dotted-decimal) equivalent.
- Add the Base-256 (dotted-decimal) equivalent to the network address/subnet zero, to determine the target subnet address.

Notes about the “target subnet”

- If you’re given subnet number x, then you use x as is to multiply by the number of addresses per subnet.
- If you’re given the n
^{ st, nd, rd, th}, subnet, e.g. 59^{th}, 343^{rd}, then you subtract one, then multiply by the number of addresses per subnet. (Because we start counting from zero.)

## Converting a Decimal Number to Base 256 (Dotted-decimal)

- How to: Convert a Decimal Number to a Base-256 Dotted-decimal
**Subnetting-WhatIsThe15thSubnetRange.pdf**

Calculations for Base-256 Conversion | |

Evaluate the # | Is the # greater than 256? |

4th Octet | . |

3rd Octet | . |

2nd Octet | . |

1st Octet | . |

~

## Do

**Review Examples: IPv4-CustomSubnetMasks-Examples-1-3.pdf****Memorize these Bit Patterns of Often Used Subnet Mask Values**(pdf)

## Do

Make sure to always have access to a calculator which has an Exponent function (^key) ( x^{y }) for **every class**.