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 Internet 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 Host 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 Network address
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 Router 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 Supernetwork
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. Routing table without supernet mask Default Network Next hop mask address address ...... 255.255.252.0. X.Y.32.0. . . . . b. Routing table with supernet mask
Forouzan Notes COSC 6377 - Fall 2000 5-23
Forouzan Notes COSC 6377 - Fall 2000 5-