Class C Subnetting
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This material was developed with funding from the
National Science Foundation under Grant # DUE 1601612
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–
Increase Subnets
IP Network Subnetting
+
1 Network
65,535 host
Click the +/- buttons to increase and decrease the number of subnets.
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Decrease Subnets
IP subnetting allows an organization or user to take a large IP network and divide it into several smaller networks called subnets. To increase the number of networks, click the button, Increase Subnets. Continued clicks will add to the number of networks but will decrease the number of hosts per network. Click the Decrease Subnets button to reduce the number of subnets.
2 Networks
32,767 hosts
4 Networks
16,383 hosts
8 Networks
8,192 hosts
A router determines the subnet size based on the subnet mask so that the network will have the correct number of subnets. Let’s look at a Class C subnet. You borrow bits from the left side of the host portion of the mask to create subnets. The number of bits borrowed or changed from a “0” to a “1” determines the number of subnets that can be created from the original network. Use the slider to change the number of bits to borrow. The remaining bits represent the number of hosts per subnet.
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Drag the slider to view the number of bits borrowed.
Borrowing Bits
The number of hosts created is determined by counting the remaining host bits, converting to decimal, and subtracting the two unusable addresses.
Use the slider to see the effect of borrowing bits from the subnet mask. Move the slider to the right to increase the number of bits borrowed, slide it to the left to decrease the bits borrowed.
Not allowed in Class “C” network
Drag the slider to view the number of subnets and host.
Subnet Mask Slider
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Fill in the blanks below.
Test Your Knowledge 1 of 6
Borrowed Bit Count =
Mask = . . .
Number of Subnets =
Hosts per Subnet =
Try Again!
Correct!
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Element
with Audio
HTML
Hint: Borrow 3 (1) leave 5 (0)
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Broadcast
Address
Default Network
Network Address = 192.100.1.0
Broadcast Address = 192.100.1.255
Usable
Addresses
Network
Address
Click each item for more detailed information.
Usable Addresses = 192.100.1.1 thru 192.100.1.254
Full Class C Network No Subnets
Size = 256 addresses 0-255
Default Subnet Mask = 255.255.255.0
Cannot use first address 192.100.1.0 or last address 192.100.1.255
Usable Addresses = 192.100.1.1 thru 192.100.1.254
Hint: Borrow 6 (1) leave 2 (0)
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Borrowed Bit Count =
Mask = . . .
Number of Subnets =
Hosts per Subnet =
Test Your Knowledge 2 of 6
Test Your Knowledge 3 of 6
Hint: Borrow 5 (1) leave 3 (0)
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Borrowed Bit Count =
Mask = . . .
Number of Subnets =
Hosts per Subnet =
Borrowed Bit Count =
Mask = . . .
Number of Subnets =
Hosts per Subnet =
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Test Your Knowledge 4 of 6
Hint: Borrow 2 (1) leave 6 (0)
Hint: Borrow 7 (1) leave 1 (0)
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Test Your Knowledge 5 of 6
Borrowed Bit Count =
Mask = . . .
Number of Subnets =
Hosts per Subnet =
Test Your Knowledge 6 of 6
Hint: Borrow 4 (1) leave 4 (0)
Borrowed Bit Count =
Mask = . . .
Number of Subnets =
Hosts per Subnet =
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Subnetting an IP network requires changing the subnet mask. If you borrow one host bit from the default mask, the result is two subnets—each subnet has one-half the number of hosts.
Take the Default Subnet Mask of 255.255.255.0. Borrowing 1 bit gives you a new mask of 255.255.255.128.
The binary equivalent is 11111111.11111111.11111111.10000000.
The decimal conversion is: 128+0+0+0+0+0+0+0=128.
Usable Addresses = 192.100.1.129 thru 192.100.1.254
Network: 192.100.1.0 (Reserved)
Mask: 255.255.255.128
Broadcast: 192.100.1.127 (Reserved)
Host Addresses:
192.100.1.1 – 192.100.1.126
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Usable Addresses = 192.100.1.1 thru 192.100.1.126
Broadcast Address = 192.100.1.127
Network: 192.100.1.128 (Reserved)
Mask: 255.255.255.128
Broadcast: 192.100.1.255 (Reserved)
Host Addresses:
192.100.1.129 – 192.100.1.254
Network Address = 192.100.1.128
Two Subnets
Subnet 1
Subnet 2
To subnet a Class C network into four subnets requires you to borrow two host bits from the default mask. Each additional bit borrowed doubles the number of subnets.
The Default Subnet Mask is 255.255.255.0 and borrowing 2 bits gives you a new mask of 255.255.255.192.
The binary equivalent is 11111111.11111111.11111111.11000000.
The decimal conversion is: 128+64+0+0+0+0+0+0=192
Broadcast Address
192.100.1.127
Network Address
192.100.1.128
256/4=64
0
64
128
192
Broadcast Address
192.100.1.255
Multiplier
Network Address
192.100.1.192
Network Address
192.100.1.0
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Subnet 3
Usable Addresses
192.100.1.165 – 192.100.1.126
Network: 192.100.1.0 (Reserved)
Mask: 255.255.255.192
Broadcast: 192.100.1.63 (Reserved)
Host Addresses:
192.100.1.1-192.100.1.62
Network:192.100.1.64 (Reserved)
Mask: 255.255.255.192
Broadcast: 192.100.1.127 (Reserved)
Host Addresses:
192.100.1.65-192.100.1.126
Subnet 4
Four Subnets
Usable Addresses
192.100.1.1 – 192.100.1.62
Network: 192.100.1.128 (Reserved)
Mask: 255.255.255.192
Broadcast: 192.100.1.191 (Reserved)
Host Addresses:
192.100.1.129-192.100.1.190
Usable Addresses
192.100.1.129 – 192.100.1.190
Broadcast Address
192.100.1.63
Network: 192.100.1.192 (Reserved)
Mask:255.255.255.192
Broadcast: 192.100.1.255 (Reserved)
Host Addresses:
192.100.1.193-192.100.1.254
Network Address
192.100.1.64
Broadcast Address
192.100.1.191
Usable Addresses
192.100.1.193 – 192.100.1.254
192.100.1.255
Subnet
1
192.100.1.224
Subnet
8
192.100.1.127
Network: 192.100.1.192 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.223 (Reserved)
Host Addresses:
192.100.1.193-192.100.1.222
192.100.1.1 – 192.100.1.30
Network: 192.100.1.224 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.255 (Reserved)
Host Addresses:
192.100.1.225-192.100.1.254
192.100.1.0
192.100.1.97 – 192.100.1.126
192.100.1.159
192.100.1.63
256/8=32
0
32
64
96
128
160
192
224
192.100.1.33 – 192.100.1.62
Subnet
2
192.100.1.129 – 192.100.1.158
192.100.1.96
Network: 192.100.1.32 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.63 (Reserved)
Host Addresses:
192.100.1.33-192.100.1.62
Subnet
3
192.100.1.65 – 192.100.1.94
192.100.1.191
Network: 192.100.1.0 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.31 (Reserved)
Host Addresses:
192.100.1.1-192.100.1.30
Subnet
4
Network: 192.100.1.64 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.95 (Reserved)
Host Addresses:
192.100.1.65-192.100.1.94
192.100.1.161 – 192.100.1.190
192.100.1.31
192.100.1.128
Network: 192.100.1.96 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.127 (Reserved)
Host Addresses:
192.100.1.97-192.100.1.126
Subnet
5
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192.100.1.32
192.100.1.193 – 192.100.1.222
192.100.1.223
192.100.1.192
192.100.1.95
Subnet
6
Network: 192.100.1.128 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.159 (Reserved)
Host Addresses:
192.100.1.129-192.100.1.158
192.100.1.225 – 192.100.1.254
Subnet
7
192.100.1.160
Network: 192.100.1.160 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.191 (Reserved)
Host Addresses:
192.100.1.161-192.100.1.190
Eight Subnets
192.100.1.64
To subnet a Class C network into eight subnets requires you to borrow three host bits from the default mask 255.255.255.0 resulting in a new mask of 255.255.255.224.
The binary equivalent is 11111111.11111111.11111111.11100000.
The decimal conversion is: 128+64+32+0+0+0+0+0=224
Subnet Eleven
Network: 192.100.1.160 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.175 (Reserved)
Host Addresses:
192.100.1.161-192.100.1.174
To subnet a Class C network into sixteen subnets requires you to borrow four host bits from the default mask 255.255.255.0 resulting in a new mask of 255.255.255.240.
The binary equivalent is 11111111.11111111.11111111.11110000.
The decimal conversion is: 128+64+32+16+0+0+0+0=240
Subnet Twelve
Network: 192.100.1.176 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.191 (Reserved)
Host Addresses:
192.100.1.177-192.100.1.190
Click each subnet for more detailed information.
Subnet
16
Subnet One
Networks: 192.100.1.0 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.31 (Reserved)
Host Addresses:
192.100.1.1-192.100.1.30
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Subnet
15
Subnet Nine
Network: 192.100.1.128 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.143 (Reserved)
Host Addresses:
192.100.1.129-192.100.1.142
Subnet One
Network: 192.100.1.0 (Reserved)
Mask: 255.255.255.224
Broadcast: 192.100.1.31 (Reserved)
Host Addresses:
192.100.1.1-192.100.1.30
Subnet Thirteen
Network: 192.100.1.192 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.207 (Reserved)
Host Addresses:
192.100.1.193-192.100.1.206
Subnet Five
Network: 192.100.1.64 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.79 (Reserved)
Host Addresses:
192.100.1.65-192.100.1.78
Subnet Three
Network: 192.100.1.32 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.47 (Reserved)
Host Addresses:
192.100.1.33-192.100.1.46
Subnet
10
Subnet Six
Network: 192.100.1.80 (Reserved)
Mask 255.255.255.240
Broadcast: 192.100.1.95 (Reserved)
Host Addresses:
192.100.1.81-192.100.1.94
Subnet Fourteen
Network: 192.100.1.208 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.223 (Reserved)
Host Addresses:
192.100.1.209-192.100.1.222
Subnet
9
Sixteen Subnets
Subnet Ten
Network: 192.100.1.144 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.159 (Reserved)
Host Addresses:
192.100.1.145-192.100.1.158
Subnet
11
Subnet Two
Networks: 192.100.1.16 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.31 (Reserved)
Host Addresses:
192.100.1.17-192.100.1.30
Subnet
13
Subnet Seven
Network: 192.100.1.96 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.111 (Reserved)
Host Addresses:
192.100.1.97-192.100.1.110
Subnet Fifteen
Network: 192.100.1.224 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.239 (Reserved)
Host Addresses:
192.100.1.225-192.100.1.238
Subnet Four
Network: 192.100.1.48 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.63 (Reserved)
Host Addresses:
192.100.1.49-192.100.1.62
Subnet
12
Subnet Eight
Network: 192.100.1.112 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.127 (Reserved)
Host Addresses:
192.100.1.113-192.100.1.126
Subnet Sixteen
Network: 192.100.1.240 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.255 (Reserved)
Host Addresses:
192.100.1.241-192.100.1.254
Subnet
14
Subnet One
Network: 192.100.1.0 (Reserved)
Mask: 255.255.255.240
Broadcast: 192.100.1.15 (Reserved)
Host Addresses:
192.100.1.1-192.100.1.14
Subnet Twenty Three
Network: 192.100.1.176 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.183 (Reserved)
Host Addresses:
192.100.1.177-192.100.1.182
Subnet Eighteen
Network: 192.100.1.136 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.143 (Reserved)
Host Addresses:
192.100.1.137-192.100.1.142
Subnet
28
Subnet Twenty One
Network: 192.100.1.160 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.167 (Reserved)
Host Addresses:
192.100.1.161-192.100.1.166
Subnet Sixteen
Network: 192.100.1.120 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.127 (Reserved)
Host Addresses:
192.100.1.121-192.100.1.126
Subnet
27
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Subnet
32
Subnet Nineteen
Network: 192.100.1.144 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.151 (Reserved)
Host Addresses:
192.100.1.145-192.100.1.150
Subnet Fourteen
Network: 192.100.1.104 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.111 (Reserved)
Host Addresses:
192.100.1.105-192.100.1.110
Subnet Nine
Network: 192.100.1.64 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.71 (Reserved)
Host Addresses:
192.100.1.63-192.100.1.70
Subnet Seventeen
Network: 192.100.1.128 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.135 (Reserved)
Host Addresses:
192.100.1.129-192.100.1.134
Subnet Seven
Network: 192.100.1.48 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.1.55 (Reserved)
Host Addresses:
192.100.1.49-192.100.1.54
Subnet One
Network: 192.100.1.0 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.7 (Reserved)
Host Addresses:
192.100.1.1-192.100.1.6
Subnet Fifteen
Network: 192.100.1.112 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.119 (Reserved)
Host Addresses:
192.100.1.113-192.100.1.118
Subnet Eleven
Network: 192.100.1.80 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.87 (Reserved)
Host Addresses:
192.100.1.81-192.100.1.86
Subnet
30
Subnet Ten
Network: 192.100.1.72 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.79 (Reserved)
Host Addresses:
192.100.1.73-192.100.1.78
Subnet Five
Network: 192.100.1.32 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.39 (Reserved)
Host Addresses:
192.100.1.33-192.100.1.38
To subnet a Class C network into thirty-two subnets requires you to borrow five host bits from the default mask of 255.255.255.0 resulting in a new mask of 255.255.255.248.
The binary equivalent is 11111111.11111111.11111111.11111000.
The decimal conversion is: 128+64+32+16+8+0+0+0=248
Subnet Thirteen
Network: 192.100.1.96 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.103 (Reserved)
Host Addresses:
192.100.1.97-192.100.1.102
Subnet Eight
Network: 192.100.1.56 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.63 (Reserved)
Host Addresses:
192.100.1.57-192.100.1.62
Subnet Three
Network: 192.100.1.16 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.23 (Reserved)
Host Addresses:
192.100.1.17-192.100.1.22
Subnet
26
Subnet Twelve
Network: 192.100.1.88 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.95 (Reserved)
Host Addresses:
192.100.1.89-192.100.1.94
Subnet Six
Network: 192.100.1.40 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.47 (Reserved)
Host Addresses:
192.100.1.41-192.100.1.46
Subnet
21
Subnet
25
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Subnet
29
Subnet Four
Network: 192.100.1.24 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.31 (Reserved)
Host Addresses:
192.100.1.25-192.100.1.30
Subnet
22
Subnet
18
Subnet Two
Network: 192.100.1. 8 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1. 15 (Reserved)
Host Addresses:
192.100.1.9-192.100.1.14
Subnet Twenty Eight
Network: 192.100.1.216 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.223 (Reserved)
Host Addresses:
192.100.1.217-192.100.1.222
Subnet
23
Subnet
19
Subnet Thirty Two
Network: 192.100.1.248 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.255 (Reserved)
Host Addresses:
192.100.1.249-192.100.1.254
Subnet Twenty Six
Network: 192.100.1.200 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.207 (Reserved)
Host Addresses:
192.100.1.201-192.100.1.206
Subnet
24
Subnet
20
Subnet Thirty
Network: 192.100.1.232 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.239 (Reserved)
Host Addresses:
192.100.1.231-192.100.1.238
Subnet Twenty Nine
Network: 192.100.1.224 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.231 (Reserved)
Host Addresses:
192.100.1.225-192.100.1.230
Subnet Twenty Four
Network: 192.100.1.184 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.191 (Reserved)
Host Addresses:
192.100.1.185-192.100.1.190
Subnet Twenty Seven
Network: 192.100.1.208 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.215 (Reserved)
Host Addresses:
192.100.1.209-192.100.1.214
Subnet
17
Subnet Twenty Two
Network: 192.100.1.168 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.175 (Reserved)
Host Addresses:
192.100.1.169-192.100.1.174
Subnet Thirty One
Network: 192.100.1.240 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.247 (Reserved)
Host Addresses:
192.100.1.241-192.100.1.246
Subnet Twenty Five
Network: 192.100.1.192 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.199 (Reserved)
Host Addresses:
192.100.1.193-192.100.1.198
Subnet Twenty
Network: 192.100.1.152 (Reserved)
Mask: 255.255.255.248
Broadcast: 192.100.1.159 (Reserved)
Host Addresses:
192.100.1.153-192.100.1.158
Subnet
31
Thirty-two Subnets
Subnet Challenge 1
Default Subnet Mask = 255.255.255.0
New Mask = 255.255.255.128
Binary = 11111111.11111111.11111111.10000000
Subnet Two
Network: 192.100.1.
Mask: 255.255.255.128
Broadcast: 192.100.1.
Host Addresses:
192.100.1.129 – 192. 100.1.254
Subnet One
Network: 192.100.1.
Mask: 255.255.255.128
Broadcast: 192.100.1.
Host Addresses:
192.100.1.1 – 192. 100.1.126
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Subnet Three
Network: 192.100.1.
Mask: 255.255.255.192
Broadcast: 192.100.1.
Host Addresses:
192.100.1.129 – 192. 100.1.190
Subnet Challenge 2
Subnet One
Network: 192.100.1.0
Mask: 255.255.255.192
Broadcast: 192.100.1.
Host Addresses:
192.100.1.1 – 192. 100.1.62
Default Subnet Mask = 255.255.255.192
New Mask = 255.255.255.192
Binary = 11111111.11111111.11111111.11000000
Subnet Four
Network: 192.100.1.
Mask: 255.255.255.
Broadcast: 192.100.1.
Host Addresses:
192.100.1. –
192. 100.1.
Subnet Two
Network: 192.100.1.64
Mask: 255.255.255.192
Broadcast: 192.100.1.127
Host Addresses:
192.100.1. –
192. 100.1.
18/19
Subnet Six
Network: 192.100.1.160
Mask: 255.255.255.224
Broadcast: 192.100.1.191
Host Addresses:
192.100.1. –
192. 100.1.
Subnet Challenge 3
Subnet Seven
Network: 192.100.1.192
Mask: 255.255.255.224
Broadcast: 192.100.1.223
Host Addresses:
192.100.1. –
192. 100.1.
Subnet One
Network: 192.100.1.0
Mask: 255.255.255.
Broadcast: 192.100.1.
Host Addresses:
192.100.1.1 – 192. 100.1.30
Subnet Eight
Network: 192.100.1.224
Mask: 255.255.255.224
Broadcast: 192.100.1.255
Host Addresses:
192.100.1. –
192. 100.1.
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Subnet Two
Network: 192.100.1.
Mask: 255.255.255.
Broadcast: 192.100.1.
Host Addresses:
192.100.1.33 – 192. 100.1.62
Subnet Three
Network: 192.100.1.
Mask: 255.255.255.
Broadcast: 192.100.1.
Host Addresses:
192.100.1.65 – 192. 100.1.94
Default Subnet Mask = 255.255.255.224
New Mask = 255.255.255.224
Binary = 11111111.11111111.11111111.11100000
Subnet Four
Network: 192.100.1.
Mask: 255.255.255.
Broadcast: 192.100.1.
Host Addresses:
192.100.1.97 – 192. 100.1.126
Subnet Five
Network: 192.100.1.128
Mask: 255.255.255.224
Broadcast: 192.100.1.159
Host Addresses:
192.100.1. –
192. 100.1.