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# Welcome to Back! - PowerPoint PPT Presentation

Welcome to Back!. TCP/IP Subnetting. Pop Quiz. TCP/IP Cheat Sheet. IP Addresses. My localhost -&gt; 192.168.5.201 www.yahoo.com -&gt; 87.248.113.14 . IP Addresses. Every IP Address has a node portion and a network portion. IP Address: 192.168.5.201

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### TCP/IP Subnetting

Pop Quiz

TCP/IP Cheat Sheet

• My localhost -> 192.168.5.201
• www.yahoo.com -> 87.248.113.14
• Every IP Address has a node portion and a network portion

Network Portion: 192.168.5.201

Node Portion: 192.168.5.201

• The subnet mask tells us which part of an IP address is the node portion vs. the network portion

----------------------------------------------------

Network ID: 192.168.5.0

Binary ANDing
• AND is a mathematical operator just like

+ (plus) and – (minus)

• 1 + 1 = 2
• 1 AND 1 = 1
AND Truth Table

A | B | A AND B

---------------------------------------

FALSE | FALSE | FALSE

FALSE | TRUE | FALSE

TRUE | FALSE | FALSE

TRUE | TRUE | TRUE

AND Truth Table

A B A AND B

-----------------------------

0 0 0

0 1 0

1 0 0

1 1 1

AND Truth Table

0 AND 0 = 0

0 AND 1 = 0

1 AND 0 = 0

1 AND 1 = 1

Man vs Machine
• Human readable dotted decimal notation

192.168.5.201

• Each number represents an “Octet” or 8 bits
• What the computer sees:

11000000.10101000.00000101.11001001

11000000101010000000010111001001

• IP: 192.168.5.201
• Subnet: 255.255.255.0

IP: 11000000.10101000.00000101.11001001

Subnet: 11111111.11111111.11111111.00000000

-----------------------------------------------

11000000.10101000.00000101.00000000

IP: 11000000.10101000.00000101.11001001

Subnet: 11111111.11111111.11111111.00000000

-----------------------------------------------

11000000.10101000.00000101.00000000

AND

TCP/IP Cheat Sheet: The Rules
• The Subnet/network address is always hidden behind the 1s in the mask

IP: 11000000.10101000.00000101.11001001

Subnet: 11111111.11111111.11111111.00000000

-----------------------------------------------

11000000.10101000.00000101.00000000

TCP/IP Cheat Sheet: The Rules
• The Host/Node address is always hidden behind the 0s in the mask

IP: 11000000.10101000.00000101.11001001

Subnet: 11111111.11111111.11111111.00000000

-----------------------------------------------

11000000.10101000.00000101.00000000

TCP/IP Cheat Sheet: The Rules

(Except in special cases)

• The all-1s and all-0s subnet addresses are invalid (but NOT in CIDR)

Ex.

Network ID 192.168.1.0

11111111.11111111.11111111.10000000

192.168.1.250= .11111010

--------------

10000000

192.168.1.5= .00000101

--------------

00000000

These bits belong to the Big IP in the Sky

(we can’t change them)

These are the bits that we own

Breaks the rule! (except in CIDR)

TCP/IP Cheat Sheet: The Rules

(Except in special cases)

• The all-1s and all-0s host addresses are invalid (Always)

Ex.

OR

Reason Behind the Rule
• The all zeros host address is the same as the network ID

Ex. IP: 192.168.1.0

Subnet: 255.255.255.0

----------------------------------------

Network ID: 192.168.1.0