IP SUBNETTING

Download IP Subnetting. (Week 4, Wednesday ... Subnetting a class C network. ▫ Suppose the ... Using the IP Subnet Calculator, determine the maximum...

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IP Subnetting (Week 4, Wednesday 1/31/2007)

© Abdou Illia, Spring 2007

Structure of IP addresses

Network Part (n)

Local Part (h) Sgmt. part Host part

Class A

nnnnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh

10.0.0.1 – 126.255.255.255

Class B

nnnnnnnn.nnnnnnnn.hhhhhhhh.hhhhhhhh

128.0.0.1 – 191.255.255.255

Class C

nnnnnnnn.nnnnnnnn.nnnnnnnn.hhhhhhhh

192.0.0.1 – 223.255.255.255

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Reserved IP addresses IP addresses reserved for private use. Class

Range

A

10.0.0.0 – 10.255.255.255

B

172.16.0.0 – 172.31.255.255

C

192.168.0.0 – 192.168.255.255 Special IP addresses.

Address

Use

255.255.255.255 Example: 10.255.255.255

Local broadcast to LAN computers Broadcast to network 10.0.0.0/8

127.0.0.1

Loopback address (for self addressing)

0.0.0.0

Prohibited

169.254.x.x

Automatic Private IP Addressing

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Structure of IP addresses Segment Part

Network Part

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Host Part

The division between Network part, Segment part, and Host part is determined by a computer or a router by using a network mask. 4

Network mask „

A 32 bit number, just like an IP address, where all bits in the Network Part and the Segment Part are set to 1, and all bits in the Host Part are set to 0. Example: 11111111 11111111 11111111 00000000 (or 255.255.255.0 in decimal notation)

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Computers use Network mask, along with the IP address, to determine whether or not a destination IP address is on the same logical network. 5

Two Virtual LANs 192.168.2.1 255.255.255.0

192.168.1.1 255.255.255.0

192.168.1.2 255.255.255.0

192.168.1.3 255.255.255.0

192.168.2.2 255.255.255.0

Switch

192.168.2.3 255.255.255.0

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Two interconnected LANs

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128 64 32 „ Are the following three Class C IP addresses 16 8 from the same network? 4 192.168.1.1, 192.168.1.50 and 192.168.2.1 2 IP: 11000000 10101000 00000001 00000001 192.168.1.1 1

The ADDing technique

Mask:

11111111

11111111

11111111

00000000

255.255.255.0

Network:

11000000

10101000

00000001

00000000

192.168.1.0/24

IP:

11000000

10101000

00000001

00110010

192.168.1.50

Mask:

11111111

11111111

11111111

00000000

255.255.255.0

Network:

11000000

10101000

00000001

00000000

192.168.1.0/24

IP:

11000000

10101000

00000010

00000001

192.168.2.1

Mask:

11111111

11111111

11111111

00000000

255.255.255.0

Network:

11000000

10101000

00000010

00000000

192.168.2.0/24

Network 1: 192.168.1.0/24, i.e network starting at 192.168.1.0 with network mask 255.255.255.0. 8 Network 2: 192.168.2.0/24, i.e network starting at 192.168.2.0 with network mask 255.255.255.0.

Subnetting a class C network „ „ ¾

128 64 32 16 8 4 2 1

Suppose the 192.168.1.0/24 network You want to divide that network into two segments You can decide to use the first bit of the fourth octet as dividing point between your network segments. So, your network mask would be:

11111111 11111111 11111111 10000000 And you will have about 27 = 128 hosts in each segment. Segment 1: 192.168.1.0 to 192.168.1.127 Segment 2: 192.168.1.128 to 192.168.1.255

How to determine the two segments using the ADDing technique?

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Subnetting a class C network Segment 1: 192.168.1.0 to 192.168.1.127

128 64 32 16 8 4 2 1

IP:

11000000

10101000

00000001

00000001

192.168.1.1

Mask:

11111111

11111111

11111111

10000000

255.255.255.128

Network:

11000000

10101000

00000001

00000000

192.168.1.0/25

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IP:

11000000

10101000

00000001

01111111

192.168.1.127

Mask:

11111111

11111111

11111111

10000000

255.255.255.128

Network:

11000000

10101000

00000001

00000000

192.168.1.0/25 10

Subnetting a class C network Segment 2: 192.168.1.128 to 192.168.1.255

128 64 32 16 8 4 2 1

IP:

11000000

10101000

00000001

10000000

192.168.1.128

Mask:

11111111

11111111

11111111

10000000

255.255.255.128

Network:

11000000

10101000

00000001

10000000

192.168.1.128/25

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IP:

11000000

10101000

00000001

11111110

192.168.1.254

Mask:

11111111

11111111

11111111

10000000

255.255.255.128

Network:

11000000

10101000

00000001

10000000

192.168.1.128/25 11

Question 1 „

Network A is IP network 192.168.1.x/24 (i.e a Class C network with a default 24-bit mask). Using the IP Subnet Calculator, determine the maximum number of hosts (computers) in each of the Network A’s subnets assuming that there are two subnets. You answer: ________.

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Using the IP Subnet Calculator, determine the maximum number of subnets for a Class B network assuming that the four first bits of the third octet in each IP address are used as subnet bits. Your answer: _____. What is the maximum number of computers for each subnet? Your answer: ______. 12

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