# Welcome to Back! TCP/IP Subnetting Pop Quiz TCP/IP Cheat Sheet.

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Welcome to Back!

TCP/IP Subnetting

Pop Quiz TCP/IP Cheat Sheet

IP Addresses My localhost -> 192.168.5.201 www.yahoo.com -> 87.248.113.14www.yahoo.com

IP Addresses IP Address: 192.168.5.201 Network Portion: 192.168.5.201 Node Portion: 192.168.5.201 Every IP Address has a node portion and a network portion

Subnet Mask IP Address: 192.168.5.201 Subnet Mask: 255.255.255.0 ---------------------------------------------------- Network ID: 192.168.5.0 The subnet mask tells us which part of an IP address is the node portion vs. the network portion An IP address without a subnet mask is meaningless

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 ----------------------------- 000 010 100 11 1

AND Truth Table 0 AND 0 = 0 0 AND 1 = 0 1 AND 0 = 0 1 AND 1 = 1

11000000101010000000010111001001 11000000.10101000.00000101.11001001 Man vs Machine Human readable dotted decimal notation 192.168.5.201 –Each number represents an “Octet” or 8 bits What the computer sees:

Subnet Mask and ANDing IP:192.168.5.201 Subnet: 255.255.255.0 IP: 11000000.10101000.00000101.11001001 Subnet: 11111111.11111111.11111111.00000000 ----------------------------------------------- 11000000.10101000.00000101.00000000 AND IP: 11000000.10101000.00000101.11001001 Subnet: 11111111.11111111.11111111.00000000 ----------------------------------------------- 11000000.10101000.00000101.00000000

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

192.168.1.250=.11111010 -------------- 10000000 192.168.1.5=.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 Subnet Mask 255.255.255.128 -> 11111111.11111111.11111111.10000000 0s hide the host address 1s hide the subnet address Breaks the rule! ( except in CIDR ) These bits belong to the Big IP in the Sky (we can’t change them) These are the bits that we own

TCP/IP Cheat Sheet: The Rules (Except in special cases) The all-1s and all-0s host addresses are invalid (Always) Ex. IP Address: 192.168.1.0 Subnet Mask:255.255.255.0 OR IP Address: 192.168.1.255 Subnet Mask:255.255.255.0

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 The all ones host address is reserved for the broadcast address

Practice Problems 1 AND 1 1 AND 0 0 AND 1 0 AND 0 1111 AND 1010 0000 AND 1010 110101 AND 1101110

Practice Problems 110010b to Decimal 137d to Binary

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