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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 -> 87.248.113.14 . IP Addresses. Every IP Address has a node portion and a network portion. IP Address: 192.168.5.201
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Pop Quiz TCP/IP Cheat Sheet
IP Addresses • My localhost -> 192.168.5.201 • www.yahoo.com -> 87.248.113.14
IP Addresses • Every IP Address has a node portion and a network portion IP Address: 192.168.5.201 Network Portion: 192.168.5.201 Node Portion: 192.168.5.201
Subnet Mask • 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 IP Address: 192.168.5.201 Subnet Mask:255.255.255.0 ---------------------------------------------------- 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
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 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. 0s hide the host address Network ID 192.168.1.0 Subnet Mask 255.255.255.128 -> 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 1s hide the subnet address 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. 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