IP Subnetting – Solution

 

For the solution, focus in on the interesting octet, the octet in the mask that is not all one’s or all zero’s.  Convert the interesting octet into binary for both the address and mask and do a logical AND ( 1 + 1 = 1; 0 + anything = 0 ), this is the subnet or wire address.  To help keep the host bits verses the network/subnet bits straight, draw a line after the last one in the mask.  For the broadcast of the subnet, change all the host bits (bits to the right of the line) to ones.  To come up with the range of valid addresses (first and last host addresses), set all bits, except the least significant bit to zero.  The least significant bit should be set to a one, this is the first address in the subnet.  Reverse those bits, in other words, change all the host bits to ones, except the least significant…that one should be set to a zero.  That is the last address in the subnet.  For the number of host addresses in a subnet, use the formula 2n – 2 (where n = number of host bits).

Example:

Address

172

16

37

186

Mask

255

255

255

192

Address in Binary

 

 

 

10

11 1010

Mask in Binary

 

 

 

11

00 0000

Subnet in Binary

 

 

 

10

00 0000

Broadcast in Binary

 

 

 

10

11 1111

First Address in Binary

 

 

 

10

00 0001

Last Address in Binary

 

 

 

10

11 1110

Subnet

172

16

37

128

Broadcast

172

16

37

191

First Address

172

16

37

129

Last Address

172

16

37

190

 

Number of hosts = 26 – 2 = 64 – 2 = 62

 

172.16.37.186/26

 

 

 

Subnet

172.16.37.128

 

Broadcast

172.16.37.191

 

Number of Hosts

62

 

First Host Address

172.16.37.129

 

Last Host Address

172.16.37.190

 

           

 

                                                                                                                       

 

 

1.                  Question

 

Address

10

0

199

237

Mask

255

255

252

0

Address in Binary

 

 

1100 01 

11

 

Mask in Binary

 

 

1111 11 

00

 

Subnet in Binary

 

 

1100 01 

00

 

Broadcast in Binary

 

 

1100 01 

11

255

First Address in Binary

 

 

1100 01 

00

  1

Last Address in Binary

 

 

1100 01 

11

  254

Subnet

10

0

196

0

Broadcast

10

0

199

255

First Address

10

0

196

1

Last Address

10

0

199

254

  Number of hosts = 210 – 2 = 1024 – 2 = 1022

10.0.199.237/22

 

 

 

Subnet

10.0.196.0

 

Broadcast

10.0.199.255

 

Number of Hosts

1022

 

First Host Address

10.0.196.1

 

Last Host Address

10.0.199.254

 

           


                                                                                                                       

 

 

2.                  Question

 

Address

172

16

37

186

Mask

255

255

255

224

Address in Binary

 

 

 

101 

1 1010

Mask in Binary

 

 

 

111 

0 0000

Subnet in Binary

 

 

 

101 

0 0000

Broadcast in Binary

 

 

 

101 

1 1111

First Address in Binary

 

 

 

101 

0 0001

Last Address in Binary

 

 

 

101 

1 1110

Subnet

172

16

37

160

Broadcast

172

16

37

191

First Address

172

16

37

161

Last Address

172

16

37

190

  Number of hosts = 25 – 2 = 32 – 2 = 30

172.16.37.186/27

 

 

 

Subnet

172.16.37.160

 

Broadcast

172.16.37.191

 

Number of Hosts

30

 

First Host Address

172.16.37.161

 

Last Host Address

172.16.37.190

 

           


                                                                                                                       

 

 

3.                  Question

 

Address

192

168

14

87

Mask

255

255

255

192

Address in Binary

 

 

 

01 

01 0111

Mask in Binary

 

 

 

11 

00 0000

Subnet in Binary

 

 

 

01 

00 0000

Broadcast in Binary

 

 

 

01 

11 1111

First Address in Binary

 

 

 

01 

00 0001

Last Address in Binary

 

 

 

01 

11 1110

Subnet

192

168

14

64

Broadcast

192

168

14

127

First Address

192

168

14

65

Last Address

192

168

14

126

  Number of hosts = 26 – 2 = 64 – 2 = 62

192.168.14.87/26

 

 

 

Subnet

192.168.14.64

 

Broadcast

192.168.14.127

 

Number of Hosts

62

 

First Host Address

192.168.14.65

 

Last Host Address

192.168.14.126

 

           


                                                                                                                       

 

 

4.                  Question

 

Address

10

212

0

1

Mask

255

252

0

0

Address in Binary

 

1101 01 

00

 

 

Mask in Binary

 

1111 11 

00

 

 

Subnet in Binary

 

1101 01 

00

 

 

Broadcast in Binary

 

1101 01 

11

255 

  255

First Address in Binary

 

1101 01 

00

  0

Last Address in Binary

 

1101 01 

11

  255

254

Subnet

10

212

0

0

Broadcast

10

215

255

255

First Address

10

212

0

1

Last Address

10

215

255

254

  Number of hosts = 218 – 2 = 262144 – 2 = 262142

10.212.0.1/14

 

 

 

Subnet

10.212.0.0

 

Broadcast

10.215.255.255

 

Number of Hosts

262,142

 

First Host Address

10.212.0.1

 

Last Host Address

10.215.255.254

 

           


                                                                                                                       

 

 

5.                  Question

 

Address

172

30

32

117

Mask

255

255

255

128

Address in Binary

 

 

 

111 0101

Mask in Binary

 

 

 

000 0000

Subnet in Binary

 

 

 

000 0000

Broadcast in Binary

 

 

 

111 1111

First Address in Binary

 

 

 

000 0001

Last Address in Binary

 

 

 

111 1110

Subnet

172

30

32

0

Broadcast

172

30

32

127

First Address

172

30

32

1

Last Address

172

30

32

126

  Number of hosts = 27 – 2 = 128 – 2 = 126

172.30.32.117/25

 

 

 

Subnet

172.30.32.0

 

Broadcast

172.30.32.127

 

Number of Hosts

126

 

First Host Address

172.30.32.1

 

Last Host Address

172.30.32.126

 

           


                                                                                                                       

 

 

 

 

6.                  Question

 

Address

172

16

197

45

Mask

255

255

254

0

Address in Binary

 

 

1100 010 

1

 

Mask in Binary

 

 

1111 111 

0

 

Subnet in Binary

 

 

1100 010 

0

 

Broadcast in Binary

 

 

1100 010 

1

 255

First Address in Binary

 

 

1100 010 

0

1

Last Address in Binary

 

 

1100 010 

1

  254

Subnet

172

16

196

0

Broadcast

172

16

197

255

First Address

172

16

196

1

Last Address

172

16

197

254

Number of hosts = 29 – 2 = 512 – 2 = 510  

172.16.197.45/23

 

 

 

Subnet

172.16.196.0

 

Broadcast

172.16.197.255

 

Number of Hosts

510

 

First Host Address

172.16.196.1

 

Last Host Address

172.16.197.254

 

           

 

 


                                                                                                                       

 

 

7.                  Question

 

Address

192

168

33

33

Mask

255

255

255

252

Address in Binary

 

 

 

0010 00 

01

Mask in Binary

 

 

 

1111 11 

00

Subnet in Binary

 

 

 

0010 00 

00

Broadcast in Binary

 

 

 

0010 00 

11

First Address in Binary

 

 

 

0010 00 

01

Last Address in Binary

 

 

 

0010 00 

10

Subnet

192

168

33

32

Broadcast

192

168

33

35

First Address

192

168

33

33

Last Address

192

168

33

34

Number of hosts = 22 – 2 = 4 – 2 = 2

192.168.33.33/30

 

 

 

Subnet

192.168.33.32

 

Broadcast

192.168.33.35

 

Number of Hosts

2

 

First Host Address

192.168.33.33

 

Last Host Address

192.168.33.34

 

           


                                                                                                                       

 

 

8.                  Question

 

Address

10

191

43

101

Mask

255

255

240

0

Address in Binary

 

 

0010  

1011

 

Mask in Binary

 

 

1111  

0000

 

Subnet in Binary

 

 

0010  

0000

 

Broadcast in Binary

 

 

0010  

1111

  255

First Address in Binary

 

 

0010  

0000

1

Last Address in Binary

 

 

0010  

1111

  254

Subnet

10

191

32

0

Broadcast

10

191

47

255

First Address

10

191

32

1

Last Address

10

191

47

254

  Number of hosts = 212 – 2 = 4096 – 2 = 4094

10.191.43.101/20

 

 

 

Subnet

10.191.32.0

 

Broadcast

10.191.47.255

 

Number of Hosts

4094

 

First Host Address

10.191.32.1

 

Last Host Address

10.191.47.254

 

           


                                                                                                                       

 

 

9.                  Question

 

Address

192

168

136

14

Mask

255

255

255

248

Address in Binary

 

 

 

0000 1 

110

Mask in Binary

 

 

 

1111 1 

000

Subnet in Binary

 

 

 

0000 1 

000

Broadcast in Binary

 

 

 

0000 1 

111

First Address in Binary

 

 

 

0000 1 

001

Last Address in Binary

 

 

 

0000 1 

110

Subnet

192

168

136

8

Broadcast

192

168

136

15

First Address

192

168

136

9

Last Address

192

168

136

14

Number of hosts = 23 – 2 = 8 – 2 = 6

192.168.136.14/29

 

 

 

Subnet

192.168.136.8

 

Broadcast

192.168.136.15

 

Number of Hosts

6

 

First Host Address

192.168.136.9

 

Last Host Address

192.168.136.14

 

           


                                                                                                                       

 

 

10.              Question

 

Address

192

168

136

14

Mask

255

255

255

240

Address in Binary

 

 

 

0000  

1110

Mask in Binary

 

 

 

1111  

0000

Subnet in Binary

 

 

 

0000  

0000

Broadcast in Binary

 

 

 

0000  

1111

First Address in Binary

 

 

 

0000  

0001

Last Address in Binary

 

 

 

0000  

1110

Subnet

192

168

136

0

Broadcast

192

168

136

15

First Address

192

168

136

1

Last Address

192

168

136

14

Number of hosts = 24 – 2 = 16 – 2 = 14

192.168.136.14/28

 

 

 

Subnet

192.168.136.0

 

Broadcast

192.168.136.15

 

Number of Hosts

14

 

First Host Address

192.168.136.1

 

Last Host Address

192.168.136.14

 

           


                                                                                                                       

 

 

11.              Question

 

Address

172

16

186

37

Mask

255

255

255

192

Address in Binary

 

 

 

00 

10 0101

Mask in Binary

 

 

 

11 

00 0000

Subnet in Binary

 

 

 

00 

00 0000

Broadcast in Binary

 

 

 

00 

11 1111

First Address in Binary

 

 

 

00 

00 0001

Last Address in Binary

 

 

 

00 

11 1110

Subnet

172

16

186

0

Broadcast

172

16

186

63

First Address

172

16

186

1

Last Address

172

16

186

62

Number of hosts = 26 – 2 = 64 – 2 = 62

172.16.186.37/26

 

 

 

Subnet

172.16.186.0

 

Broadcast

172.16.186.63

 

Number of Hosts

62

 

First Host Address

172.16.186.1

 

Last Host Address

172.16.186.62

 

 

           


                                                                                                                       

 

 

12.              Question

 

Address

172

16

233

233

Mask

255

255

254

0

Address in Binary

 

 

1110 101 

1

 

Mask in Binary

 

 

1111 111 

0

 

Subnet in Binary

 

 

1110 101 

0

 

Broadcast in Binary

 

 

1110 101 

1

  255

First Address in Binary

 

 

1110 101 

0

  1

Last Address in Binary

 

 

1110 101 

1

  254

Subnet

172

16

232

0

Broadcast

172

16

233

255

First Address

172

16

232

1

Last Address

172

16

233

254

Number of hosts = 29 – 2 = 512 – 2 = 510

172.26.233.233/23

 

 

 

Subnet

172.26.232.0

 

Broadcast

172.26.233.255

 

Number of Hosts

510

 

First Host Address

172.26.232.1

 

Last Host Address

172.26.233.254

 

           


                                                                                                                       

 

 

13.              Question

 

Address

10

10

10

10

Mask

255

255

248

0

Address in Binary

 

 

0000 1  

010

 

Mask in Binary

 

 

1111 1  

000

 

Subnet in Binary

 

 

0000 1  

000

 

Broadcast in Binary

 

 

0000 1  

111

  255

First Address in Binary

 

 

0000 1  

000

  1

Last Address in Binary

 

 

0000 1  

111

254

Subnet

10

10

8

0

Broadcast

10

10

15

255

First Address

10

10

8

1

Last Address

10

10

15

254

Number of hosts = 211 – 2 = 2048 – 2 = 2046

10.10.10.10/21

 

 

 

Subnet

10.10.8.0

 

Broadcast

10.10.15.255

 

Number of Hosts

2046

 

First Host Address

10.10.8.1

 

Last Host Address

10.10.15.254

 

           


                                                                                                                       

 

 

14.              Question

 

Address

172

27

198

4

Mask

255

255

224

0

Address in Binary

 

 

110 

0 0110

 

Mask in Binary

 

 

111 

0 0000

 

Subnet in Binary

 

 

110 

0 0000

 

Broadcast in Binary

 

 

110

1 1111

  255

First Address in Binary

 

 

110 

0 0000

  1

Last Address in Binary

 

 

110 

1 1111

  254

Subnet

172

27

192

0

Broadcast

172

27

223

255

First Address

172

27

192

1

Last Address

172

27

223

254

Number of hosts = 213 – 2 = 8192 – 2 = 8190

172.27.198.4/19

 

 

 

Subnet

172.27.192.0

 

Broadcast

172.27.223.255

 

Number of Hosts

8190

 

First Host Address

172.27.192.1

 

Last Host Address

172.27.223.254

 

           


                                                                                                                       

 

 

15.              Question

 

Address

192

168

4

198

Mask

255

255

255

240

Address in Binary

 

 

 

1011  

1010

Mask in Binary

 

 

 

1100  

0000

Subnet in Binary

 

 

 

1000  

0000

Broadcast in Binary

 

 

 

1011  

1111

First Address in Binary

 

 

 

1000  

0001

Last Address in Binary

 

 

 

1011  

1110

Subnet

192

168

4

192

Broadcast

172

16

37

207

First Address

172

16

37

193

Last Address

172

16

37

206

Number of hosts = 24 – 2 = 16 – 2 = 14

192.168.4.198/28

 

 

 

Subnet

192.168.4.192

 

Broadcast

192.168.4.207

 

Number of Hosts

14

 

First Host Address

192.168.4.193

 

Last Host Address

192.168.4.206

 

           


                                                                                                                       

 

 

16.              Question

 

Address

172

16

16

186

Mask

255

255

240

0

Address in Binary

 

 

0001  

0000

 

Mask in Binary

 

 

1111  

0000

 

Subnet in Binary

 

 

0001  

0000

 

Broadcast in Binary

 

 

0001  

1111

255

First Address in Binary

 

 

0001  

0000

  1

Last Address in Binary

 

 

0001  

1111

  254

Subnet

172

16

16

0

Broadcast

172

16

31

255

First Address

172

16

16

1

Last Address

172

16

31

254

Number of hosts = 212 – 2 = 4096 – 2 = 4094

172.16.16.186/20

 

 

 

Subnet

172.16.16.0

 

Broadcast

172.16.31.255

 

Number of Hosts

4094

 

First Host Address

172.16.16.1

 

Last Host Address

172.16.31.254

 

           


                                                                                                                       

 

 

17.              Question

 

Address

10

35

67

119

Mask

255

255

128

0

Address in Binary

 

 

100 0011

 

Mask in Binary

 

 

000 0000

 

Subnet in Binary

 

 

000 0000

 

Broadcast in Binary

 

 

111 1111

  255

First Address in Binary

 

 

000 0000

 1

Last Address in Binary

 

 

111 1111

  254

Subnet

10

35

0

0

Broadcast

10

35

127

255

First Address

10

35

0

1

Last Address

10

35

127

254

Number of hosts = 215 – 2 = 32768 – 2 = 32766

10.35.67.119/17

 

 

 

Subnet

10.35.0.0

 

Broadcast

10.35.127.255

 

Number of Hosts

32,766

 

First Host Address

10.35.0.1

 

Last Host Address

10.35.127.254

 

           


                                                                                                                       

 

 

18.              Question

 

Address

10

7

13

141

Mask

255

255

240

0

Address in Binary

 

 

0000  

1101

 

Mask in Binary

 

 

1111  

0000

 

Subnet in Binary

 

 

0000  

0000

 

Broadcast in Binary

 

 

0000  

1111

  255

First Address in Binary

 

 

0000  

0000

  1

Last Address in Binary

 

 

0000  

1111

  254

Subnet

10

7

0

0

Broadcast

10

7

15

255

First Address

10

7

0

1

Last Address

10

7

15

254

Number of hosts = 212 – 2 = 4096 – 2 = 4094

10.7.13.141/20

 

 

 

Subnet

10.7.0.0

 

Broadcast

10.7.15.255

 

Number of Hosts

4094

 

First Host Address

10.7.0.1

 

Last Host Address

10.7.15.254

 

 

           


                                                                                                                       

 

 

19.              Question

 

Address

172

16

37

186

Mask

255

255

255

192

Address in Binary

 

 

 

10

11 1010

Mask in Binary

 

 

 

11

00 0000

Subnet in Binary

 

 

 

10

00 0000

Broadcast in Binary

 

 

 

10

11 1111

First Address in Binary

 

 

 

10

00 0001

Last Address in Binary

 

 

 

10

11 1110

Subnet

172

16

37

128

Broadcast

172

16

37

191

First Address

172

16

37

129

Last Address

172

16

37

190

Number of hosts = 210 – 2 = 1024 – 2 = 1022

172.16.37.186/26

 

 

 

Subnet

172.16.37.128

 

Broadcast

172.16.37.191

 

Number of Hosts

62

 

First Host Address

172.16.37.129

 

Last Host Address

172.16.37.190

 

 

           


                                                                                                                       

 

 

20.              Question

 

Address

192

168

119

85

Mask

255

255

254

0

Address in Binary

 

 

0111 011 

1

 

Mask in Binary

 

 

1111 111 

0

 

Subnet in Binary

 

 

0111 011 

0

 

Broadcast in Binary

 

 

0111 011 

1

 255

First Address in Binary

 

 

0111 011 

0

  1

Last Address in Binary

 

 

0111 011 

1

  254

Subnet

192

168

118

0

Broadcast

192

168

119

255

First Address

192

168

118

1

Last Address

192

168

119

254

Number of hosts = 29 – 2 = 512 – 2 = 510

192.168.119.85/23

 

 

 

Subnet

192.168.118.0

 

Broadcast

192.168.119.255

 

Number of Hosts

510

 

First Host Address

192.168.118.1

 

Last Host Address

192.168.119.254