Slides from TCP/IP - Forouzan

Chapter 5 Subnetting and Supernetting

• Subnetting • Masking • Examples of Subnetting • Variable-Length Subnetting • Supernetting

Forouzan Notes COSC 6377 - Fall 2000 5-1

Figure 5-1 A network with two levels of hierarchy (not subnetted)

141.14.2.105 141.14.2.21 141.14.2.20 141.14.7.96 141.14.7.95

To the rest of Network R1 the 141.14.0.0

141.14.22.64 141.14.7.44 141.14.22.9 141.14.22.8

Forouzan Notes COSC 6377 - Fall 2000 5-2

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-2 A network with three levels of hierarchy (subnetted)

141.14.2.21 141.14.2.105 141.14.2.20

141.14.7.96 141.14.7.45 141.14.2.0 141.14.7.44

To the rest of Subnetwork the Internet R1 141.14.7.0 Subnetwork Subnetwork 141.14.22.0

141.14.22.8 Site

141.14.22.9 141.14.22.64 141.14.0.0

Forouzan Notes COSC 6377 - Fall 2000 5-3

Figure 5-3 Addresses in a network with and without subnetting

141. 14 . 2. 21 Netid Hostid Network access access

a. Without subnetting 141. 14 . 2. 21 Netid Subnetid Hostid Subnetwork access Host access

b. With subnetting

Forouzan Notes COSC 6377 - Fall 2000 5-4

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-4 Hierarchy concept in a telephone number

( 408) 864- 8902 Area code Exchange Connection

Forouzan Notes COSC 6377 - Fall 2000 5-5

Figure 5-5 Masking

141.14.2.21Mask 141.14.0.0 IP address255.255.0.0

a. Without subnetting

141.14.2.21Mask 141.14.2.0 IP address255.255.255.0 Subnetwork address

b. With subnetting

Forouzan Notes COSC 6377 - Fall 2000 5-6

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-6 Applying bit-wise and operator to achieve masking

141.14.2.21 IP 10001101 00001110 00000010 00010101 address

Mask 11111111 11111111 00000000 00000000 141.14.0.0 Network address 10001101 00001110 00000000 00000000 a. Without subnetting 141.14.2.21 IP 10001101 00001110 00000010 00010101 address

Mask 11111111 11111111 11111111 00000000 141.14.2.0 Subnetwork 10001101 00001110 00000010 00000000 address b. With subnetting Forouzan Notes COSC 6377 - Fall 2000 5-7

Figure 5-7 Special addresses in subnetting

Subnetid Hostid

Any All 0s Subnetwork address

Any All 1s Broadcast to all hosts in a specific subnet

All 0s Any Subnetid all 0s

All 1s Any Subnetid all 1s

Forouzan Notes COSC 6377 - Fall 2000 5-8

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-8 Masks in example 1

Mask 255.0.0.0

Netid Hostid 1111111100000000 00000000 00000000 a. Without subnetting

Mask 255.255.192.0

Netid Subnetid Hostid 11111111 1111111111 000000 00000000

b. With subnetting

Forouzan Notes COSC 6377 - Fall 2000 5-9

Figure 5-9 Range of addresses in example 1

Special addresses Special addresses (hostid all 0s) (hostid all 1s) Special addresses (subnetid all 0s) X.0.0.0 X.0.0.1... X.0.63.254 X.0.63.255 1st subnet X.0.64.0 X.0.64.1 ... X.0.127.254 X.0.127.255 2nd subnet X.0.128.0. X.0.128.1 ... X.0.191.254 X.0.191.255. . . 1022nd subnet X.255.128.0 X.255.128.1 ... X.255.191.254 X.255.191.255 X.255.192.0 X.255.192.1... X.255.255.254 X.255.255.255 Special addresses (subnetid all 1s)

Forouzan Notes COSC 6377 - Fall 2000 5-10

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-10 Subnetworks in example 1

X.0.64.2 X.0.127.254 X.0.64.1 ... X.0.64.0 Subnetwork X.0.128.2 X.0.191.254 X.0.128.1 To the rest of ... the Internet R1 X.0.128.0 Subnetwork. . . X.255.128.2 X.255.191.254 X.255.128.1 Site ... X.255.128.0 X.0.0.0 Subnetwork

Forouzan Notes COSC 6377 - Fall 2000 5-11

Figure 5-11 Mask in example 2

Mask 255.255.0.0

Netid Hostid 11111111 11111111 00000000 00000000 a. Without subnetting

Mask 255.255.240.0

Netid Subnetid Hostid 11111111 111111111111 0000 00000000

b. With subnetting

Forouzan Notes COSC 6377 - Fall 2000 5-12

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-12 Range of addresses in example 2

Special addresses Special addresses (hostid all 0s) (hostid all 1s) Special addresses (subnetid all 0s) X.Y.0.0 X.Y.0.1 ... X.Y.15.254 X.Y.15.255 1st subnet X.Y.16.0 X.Y.16.1 ... X.Y.31.254 X.Y.31.255 2nd subnet X.Y.32.0. X.Y.32.1 ... X.Y.47.254 X.Y.47.255. . . 14th subnet X.Y.224.0 X.Y.224.1 ... X.Y.239.254 X.Y.239.255 X.Y.240.0 X.Y.240.1 ... X.Y.255.254 X.Y.255.255 Special addresses (subnetid all 1s)

Forouzan Notes COSC 6377 - Fall 2000 5-13

Figure 5-13 Subnetworks in example 2

X.Y.16.2 X.Y.31.254 X.Y.16.1 ... X.Y.16.0

Subnetwork X.Y.32.2 X.Y.47.254 X.Y.32.1 To the rest of ... the Internet R1 X.Y.32.0 Subnetwork. . . X.Y.224.2 X.Y.239.254 X.Y.224.1 ... Site X.Y.224.0 X.Y.0.0 Subnetwork

ForouzanMcGraw-Hill Notes COSC 6377 - Fall 2000 The McGraw-Hill Companies, Inc., 20005-14

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-14 Masks in example 3

Mask 255.255.255.0

Netid Hostid 11111111 11111111 11111111 00000000

a. Without subnetting

Mask 255.255.255.224

Netid SubnetidHostid 11111111 11111111 11111111 11100000

b. With subnetting

Forouzan Notes COSC 6377 - Fall 2000 5-15

Figure 5-15 Range of addresses in example 3

Special addresses Special addresses hostid all 0s hostid all 1s Special addresses subnetid all 0s X.Y.Z.0 X.Y.Z.1 ... X.Y.Z.30 X.Y.Z.31 1st subnet X.Y.Z.32 X.Y.Z.33... X.Y.Z.62 X.Y.Z.63 2nd subnet X.Y.Z.64. X.Y.Z.65 ... X.Y.Z.94 X.Y.Z.95. . . 6th subnet X.Y.Z.192 X.Y.Z.193 ... X.Y.Z.222 X.Y.Z.223 X.Y.Z.224 X.Y.Z.225 ... X.Y.Z.254 X.Y.Z.255 Special addresses subnetid all 1s

Forouzan Notes COSC 6377 - Fall 2000 5-16

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-16 Subnetworks in example 3

X.Y.Z.34 X.Y.Z.62 X.Y.Z.33 ... X.Y.Z.32

Subnetwork X.Y.Z.66 X.Y.Z.94 X.Y.Z.65 ... To the rest of the Internet R1 X.Y.Z.64 Subnetwork . . . X.Y.Z.194 X.Y.Z.222 X.Y.Z.193 Site ... X.Y.Z.0 X.Y.Z.192 Subnetwork

Forouzan Notes COSC 6377 - Fall 2000 5-17

Figure 5-17 Variable-length subnetting

Site 62 hosts X.Y.Z.0

62 hosts

First mask 255.255.255.192

62 hosts

30 hosts Second mask 255.255.255.224 30 hosts

Forouzan Notes COSC 6377 - Fall 2000 5-18

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-18

First class C address Second class C address

X.Y.32.254 X.Y.33.1 X.Y.32.2 X.Y.33.253 X.Y.32.1 X.Y.33.254

Supernetwork To the rest of R1 the Internet X.Y.32.0

X.Y.35.254 X.Y.34.1 X.Y.35.253 X.Y.34.2 X.Y.35.1 X.Y.34.254

Fourth class C address Third class C address

Forouzan Notes COSC 6377 - Fall 2000 5-19

Figure 5-19 Supernet mask Netid Hostid 11111111 11111111 11111111 00000000

Netid Subnetid Hostid 11111111 11111111 11111111 11000000

a. Subnetting 4 subnets out of 1 network

Netid Hostid 11111111 11111111 11111111 00000000

Supernetid Hostid 11111111 11111111 111111 00 00000000

b. Supernetting 1 supernet out of 4 networks

Forouzan Notes COSC 6377 - Fall 2000 5-20

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-20 Two ways of defining a supernet

X.Y.32.0 , 255.255.252.0

Same X.Y.32.0 , 1024

Forouzan Notes COSC 6377 - Fall 2000 5-21

Figure 5-21 Example of supernetting

X.Y.33.4 X.Y.39.12 xxxxxxxx yyyyyyyy 00100001 00000100 xxxxxxxx yyyyyyyy 00100111 00001100

11111111 11111111 11111100 00000000 11111111 11111111 11111100 00000000

xxxxxxxx yyyyyyyy 00100000 00000000 xxxxxxxx yyyyyyyy 00100100 00000000 X.Y.32.0 X.Y.36.0

Forouzan Notes COSC 6377 - Fall 2000 5-22

Forouzan Notes COSC 6377 - Fall 2000 5- Slides from TCP/IP - Forouzan

Figure 5-22 CIDR

Default Network Next hop mask address address 255.255.255.0 X.Y.32.0 ...... 255.255.255.0 X.Y.33.0 ...... 255.255.255.0 X.Y.34.0 ...... 255.255.255.0. X.Y.35.0. . . . . a. table without supernet mask Default Network Next hop mask address address ...... 255.255.252.0. X.Y.32.0. . . . . b. with supernet mask

Forouzan Notes COSC 6377 - Fall 2000 5-23

Forouzan Notes COSC 6377 - Fall 2000 5-