Subnet in your head

WELCOME
TO THE PATH OF SUCCESS

Subnet in your head in 90 minutes! Todd Lammle
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About Todd Lammle
• Sybex author
– More than 40 titles published on Cisco; Microsoft; and, soon, wireless certification.

• President, GlobalNet Training Inc.
– Cisco, Microsoft, Security and Wireless certification hands-on courses.www.globalnettraining.com.

• CEO, RouterSim, LLC
– Cisco and Microsoft certification software products. www.routersim.com.
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I Promise…..You can subnet in your head…..

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IP Addressing and Subnetting
WWW.GLOBALNETTRAINING.COM

IP Addressing
• Hierarchical Addressing Framework. •Network.node addressing, 32 bits (four bytes). • The Hierarchical advantage is increased ability of addresses.

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Binary Numbering
Defining basic IP addressing terms: Bit = One digit (one or a zero). Byte = Seven or eight bits (depends on parity). Octet = Always eight bits.
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Binaryto Decimal Conversion
Converting binary to decimal examples:

128 64 32 16 8 4 2 1: Bit values
0 1 0 0 1 0 0 1 0 1 0 0 0 1 0 0 0 0 0 0 1 1 0 1 1 0 0 0 1 0 0 1 1 1 0 1 0 1 1 0 1 1 0 1 1 1 1 0 =0 = 255 = 15 = 85 = 131 = 22
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Globalnet Training Inc. - CCNA/DA Copyright 2002/2003

Binary (Cont.)
Bits 0 1 2 3 4 5 6 7 8 Binary 00000000 10000000 11000000 11100000 11110000 11111000 1111110011111110 11111111 Decimal 0 128 192 224 240 248 252 254 255
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Math to Memorize!
Subnet mask 256-192 256-224 256-240 256-248 256-252 First Subnet 64 32 16 8 4

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Powers of 2
21=2 22=4 23=8 24=16 25=32 26=64 27=128 28=256
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IP Addressing
32 bits Network Host

255
1 byte

255
1 byte

255
1 byte

255
1 byte

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IP Addressing
32 bits Network Host

255
1 8 9

255
16 17

255
24 25

255
32

11111111 11111111 11111111 11111111
128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1
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GlobalnetTraining Inc. - CCNA/DA Copyright 2002/2003

IP Address Classes
8 bits 8 bits Host 8 bits Host Host 8 bits Host Host Host

Class A: Class B: Class C: Class D: Class E:

Network

Network Network

Network Network Network

Multicast Research

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IP Address Classes
Class A:
0NNNNNNN Range (1-126)

00000000 = 0 01111111 =127 10000000 =128 10111111 = 191 11000000 = 192 11011111 = 223
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Class B:

10NNNNNN Range (128-191)

Class C:

110NNNNN Range (192-223)

Note: Class D range is 224-239
Globalnet Training Inc. - CCNA/DA Copyright 2002/2003

IP Address Ranges
10.0.0.0 10.0.0.1 10.255.255.254 10.255.255.255 172.16.0.0 172.16.0.1 172.16.255.254 172.16.255.255 Network Address First valid host Lastvalid host Broadcast Address 192.168.10.0 192.168.10.1 192.168.10.254 192.168.10.255
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Globalnet Training Inc. - CCNA/DA Copyright 2002/2003

Addressing Without Subnets

172.16.0.1

172.16.0.2

172.16.255.254

Network 172.16.0.0

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Addressing With Subnets

172.16.40.0

172.16.30.0

172.16.10.0

172.16.20.0Network 172.16.0.0
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Subnet Masks
Class A default 255.0.0.0 Class B default 255.255.0.0 Class C default 255.255.255.0

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How Do You Determine the Mask?
• Count the number of subnets in the network and remember to think about growth. • Count the number of hosts in each subnet...