Subnetting Class A address Problem 1

128 |  1 0 0 0 0 0 0 0   (i.e. 1 Bit ON and 7 OFF)

192 |  1 1 0 0 0 0 0 0   (i.e. 2 Bits ON and 6 OFF)

224 |  1 1 1 0 0 0 0 0    (i.e. 3 Bits ON and 5 OFF)

240 |  1 1 1 1 0 0 0 0    (i.e. 4 Bits ON and 4 OFF)

248 |  1 1 1 1 1 0 0 0    (i.e. 5 Bits ON and 3 OFF)

252 |  1 1 1 1 1 1 0 0    (i.e. 6 Bits ON and 2 OFF)

254 |  1 1 1 1 1 1 1 0    (i.e. 7 Bits ON and 1 OFF)

255 |  1 1 1 1 1 1 1 1    (i.e. 8 Bits ON and  0 OFF)

IP Address   10.255.0.0/20

subnet Mask == 255.255.240.0

S

Subnetting Class A Intorduction

128 |  1 0 0 0 0 0 0 0   (i.e. 1 Bit ON and 7 OFF)

192 |  1 1 0 0 0 0 0 0   (i.e. 2 Bits ON and 6 OFF)

224 |  1 1 1 0 0 0 0 0    (i.e. 3 Bits ON and 5 OFF)

240 |  1 1 1 1 0 0 0 0    (i.e. 4 Bits ON and 4 OFF)

248 |  1 1 1 1 1 0 0 0    (i.e. 5 Bits ON and 3 OFF)

252 |  1 1 1 1 1 1 0 0    (i.e. 6 Bits ON and 2 OFF)

254 |  1 1 1 1 1 1 1 0    (i.e. 7 Bits ON and 1 OFF)

255 |  1 1 1 1 1 1 1 1    (i.e. 8 Bits ON and  0 OFF)

Subnet Mask                          CIDR Value

CLASS A

255.0.0.0                                  /8

255.128.0.0                              /9

255.192.0.0                            /10

255.224.0.0                            /11

255.240.0.0                            /12

255.248.0.0                            /13

255.252.0.0                            /14

255.254.0.0                            /15

Subnetting Class B Address Problem 5

Must Remind (Keep in Mind)

128 |  1 0 0 0 0 0 0 0   (i.e. 1 Bit ON and 7 OFF)

192 |  1 1 0 0 0 0 0 0   (i.e. 2 Bits ON and 6 OFF)

224 |  1 1 1 0 0 0 0 0    (i.e. 3 Bits ON and 5 OFF)

240 |  1 1 1 1 0 0 0 0    (i.e. 4 Bits ON and 4 OFF)

248 |  1 1 1 1 1 0 0 0    (i.e. 5 Bits ON and 3 OFF)

252 |  1 1 1 1 1 1 0 0    (i.e. 6 Bits ON and 2 OFF)

254 |  1 1 1 1 1 1 1 0    (i.e. 7 Bits ON and 1 OFF)

255 |  1 1 1 1 1 1 1 1    (i.e. 8 Bits ON and  0 OFF)

PROBLEM  5.

172.16.0.0 (Network Address)
255.255.248.0 (/21)

Network = 2^5 = 32
Hosts =      2^11 - 2 = 2046 ( 3 bits in 3rd octet and 8 bits in 4th octet)

valid subnets = 256-248= 8 

Block Size =  0 ,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168,176 ,184,192,200,208,216,224,232,240   

NETWORK 1

172.16.0.0  (Network ID)
172.16.0.1  (First Host)
172.16.0.2
172.16.0.3
.
.
.
172.16.7.252
172.16.7.253
172.16.7.254 (Last Host)
172.16.7.255 (Broadcast ID)

MUST READ

when the address 0.255  after that 3rd octet will be started from 1.0 then 1.1, 1.2, 1.3 similarly address reach 1.255  3rd octet will start From  2.0  Similarly  all the address will allocate in a same way. ( For Understanding the Procedure)

NETWORK  2

172.16.8.0  (Network ID)
172.16.8.1  (First Host)
172.16.8.2
172.16.8.3
.
.
.
172.16.15.252
172.16.15.253
172.16.15.254  (Last Host)
172.16.15.255  (Broadcast ID)

NETWORK  3

172.16.16.0  (Network ID)
172.16.16.1  (First Host)
172.16.16.2
172.16.16.3
.
.
.
172.16.23.252
172.16.23.253
172.16.23.254  (Last Host)
172.16.23.255  (Broadcast ID)

NETWORK  4

172.16.24.0  (Network ID)
172.16.24.1  (First Host)
172.16.24.2
172.16.24.3
.
.
.
172.16.31.252
172.16.31.253
172.16.31.254  (Last Host)

172.16.31.255  (Broadcast ID)

NETWORK  5

172.16.32.0  (Network ID)
172.16.32.1  (First Host)
172.16.32.2
172.16.32.3
.
.
.
172.16.39.252
172.16.39.253
172.16.39.254  (Last Host)

172.16.39.255  (Broadcast ID)

NETWORK  6

172.16.40.0  (Network ID)
172.16.40.1  (First Host)
172.16.40.2
172.16.40.3
.
.
.
172.16.47.252
172.16.47.253
172.16.47.254  (Last Host)

172.16.47.255  (Broadcast ID)

NETWORK  7

172.16.48.0  (Network ID)
172.16.48.1  (First Host)
172.16.48.2
172.16.48.3
.
.
.
172.16.55.252
172.16.55.253
172.16.55.254  (Last Host)

172.16.55.255  (Broadcast ID)

NETWORK  8

172.16.56.0  (Network ID)
172.16.56.1  (First Host)
172.16.56.2
172.16.56.3
.
.
.
172.16.63.252
172.16.63.253
172.16.63.254  (Last Host)

172.16.63.255  (Broadcast ID)

NETWORK  9

172.16.64.0  (Network ID)
172.16.64.1  (First Host)
172.16.64.2
172.16.64.3
.
.
.
172.16.71.252
172.16.71.253
172.16.71.254  (Last Host)

172.16.71.255  (Broadcast ID)

NETWORK  10

172.16.72.0  (Network ID)
172.16.72.1  (First Host)
172.16.72.2
172.16.72.3
.
.
.
172.16.739.252
172.16.79.253
172.16.79.254  (Last Host)

172.16.79.255  (Broadcast ID)

NETWORK  11

172.16.80.0  (Network ID)
172.16.80.1  (First Host)
172.16.80.2
172.16.80.3
.
.
.
172.16.87.252
172.16.87.253
172.16.87.254  (Last Host)

172.16.87.255  (Broadcast ID)

NETWORK  12

172.16.88.0  (Network ID)
172.16.88.1  (First Host)
172.16.88.2
172.16.88.3
.
.
.
172.16.95.252
172.16.95.253
172.16.95.254  (Last Host)

172.16.95.255  (Broadcast ID)

NETWORK  13

172.16.96.0  (Network ID)
172.16.96.1  (First Host)
172.16.96.2
172.16.96.3
.
.
.
172.16.103.252
172.16.103.253
172.16.103.254  (Last Host)

172.16.103.255  (Broadcast ID)

NETWORK  14

172.16.104.0  (Network ID)
172.16.104.1  (First Host)
172.16.104.2
172.16.104.3
.
.
.
172.16.111.252
172.16.111.253
172.16.111.254  (Last Host)

172.16.111.255  (Broadcast ID)

NETWORK  15

172.16.112.0  (Network ID)
172.16.112.1  (First Host)
172.16.112.2
172.16.112.3
.
.
.
172.16.119.252
172.16.119.253
172.16.119.254  (Last Host)

172.16.119.255  (Broadcast ID)

NETWORK  16

172.16.120.0  (Network ID)
172.16.120.1  (First Host)
172.16.120.2
172.16.120.3
.
.
.
172.16.127.252
172.16.127.253
172.16.127.254  (Last Host)

172.16.127.255  (Broadcast ID)

NETWORK  17

172.16.128.0  (Network ID)
172.16.128.1  (First Host)
172.16.128.2
172.16.128.3
.
.
.
172.16.135.252
172.16.135.253
172.16.135.254  (Last Host)

172.16.135.255  (Broadcast ID)

NETWORK  18

172.16.136.0  (Network ID)
172.16.136.1  (First Host)
172.16.136.2
172.16.136.3
.
.
.
172.16.143.252
172.16.143.253
172.16.143.254  (Last Host)

172.16.143.255  (Broadcast ID)

NETWORK  19

172.16.144.0  (Network ID)
172.16.144.1  (First Host)
172.16.144.2
172.16.144.3
.
.
.
172.16.151.252
172.16.151.253
172.16.151.254  (Last Host)

172.16.151.255  (Broadcast ID)

NETWORK  20

172.16.152.0  (Network ID)
172.16.152.1  (First Host)
172.16.152.2
172.16.152.3
.
.
.
172.16.159.252
172.16.159.253
172.16.159.254  (Last Host)

172.16.159.255  (Broadcast ID)

NETWORK  21

172.16.160.0  (Network ID)
172.16.160.1  (First Host)
172.16.160.2
172.16.160.3
.
.
.
172.16.167.252
172.16.167.253
172.16.167.254  (Last Host)

172.16.167.255  (Broadcast ID)

NETWORK  22

172.16.168.0  (Network ID)
172.16.168.1  (First Host)
172.16.168.2
172.16.168.3
.
.
.
172.16.175.252
172.16.175.253
172.16.175.254  (Last Host)

172.16.175.255  (Broadcast ID)

NETWORK  23

172.16.176.0  (Network ID)
172.16.176.1  (First Host)
172.16.176.2
172.16.176.3
.
.
.
172.16.183.252
172.16.183.253
172.16.183.254  (Last Host)

172.16.183.255  (Broadcast ID)

NETWORK  24

172.16.184.0  (Network ID)
172.16.184.1  (First Host)
172.16.184.2
172.16.184.3
.
.
.
172.16.191.252
172.16.191.253
172.16.191.254  (Last Host)

172.16.191.255  (Broadcast ID)

NETWORK  25

172.16.192.0  (Network ID)
172.16.192.1  (First Host)
172.16.192.2
172.16.192.3
.
.
.
172.16.199.252
172.16.199.253
172.16.199.254  (Last Host)

172.16.199.255  (Broadcast ID)

NETWORK  26

172.16.200.0  (Network ID)
172.16.200.1  (First Host)
172.16.200.2
172.16.200.3
.
.
.
172.16.207.252
172.16.207.253
172.16.207.254  (Last Host)

172.16.207.255  (Broadcast ID)

NETWORK  27

172.16.208.0  (Network ID)
172.16.208.1  (First Host)
172.16.208.2
172.16.208.3
.
.
.
172.16.215.252
172.16.215.253
172.16.215.254  (Last Host)

172.16.215.255  (Broadcast ID)

NETWORK  28

172.16.216.0  (Network ID)
172.16.216.1  (First Host)
172.16.216.2
172.16.216.3
.
.
.
172.16.223.252
172.16.223.253
172.16.223.254  (Last Host)

172.16.223.255  (Broadcast ID)

NETWORK  29

172.16.224.0  (Network ID)
172.16.224.1  (First Host)
172.16.224.2
172.16.224.3
.
.
.
172.16.231.252
172.16.231.253
172.16.231.254  (Last Host)

172.16.231.255  (Broadcast ID)

NETWORK  30

172.16.232.0  (Network ID)
172.16.232.1  (First Host)
172.16.232.2
172.16.232.3
.
.
.
172.16.239.252
172.16.239.253
172.16.239.254  (Last Host)

172.16.239.255  (Broadcast ID)

NETWORK  31

172.16.240.0  (Network ID)
172.16.240.1  (First Host)
172.16.240.2
172.16.240.3
.
.
.
172.16.247.252
172.16.247.253
172.16.247.254  (Last Host)

172.16.247.255  (Broadcast ID)

NETWORK  32

172.16.248.0  (Network ID)
172.16.248.1  (First Host)
172.16.248.2
172.16.248.3
.
.
.
172.16.255.252
172.16.255.253
172.16.255.254  (Last Host)

172.16.255.255  (Broadcast ID)

Subnetting Class B Address Problem 4

Must Remind (Keep in Mind)

128 |  1 0 0 0 0 0 0 0   (i.e. 1 Bit ON and 7 OFF)

192 |  1 1 0 0 0 0 0 0   (i.e. 2 Bits ON and 6 OFF)

224 |  1 1 1 0 0 0 0 0    (i.e. 3 Bits ON and 5 OFF)

240 |  1 1 1 1 0 0 0 0    (i.e. 4 Bits ON and 4 OFF)

248 |  1 1 1 1 1 0 0 0    (i.e. 5 Bits ON and 3 OFF)

252 |  1 1 1 1 1 1 0 0    (i.e. 6 Bits ON and 2 OFF)

254 |  1 1 1 1 1 1 1 0    (i.e. 7 Bits ON and 1 OFF)

255 |  1 1 1 1 1 1 1 1    (i.e. 8 Bits ON and  0 OFF)

PROBLEM  4.

172.16.0.0 (Network Address)
255.255.240.0 (/20)

Network = 2^4 = 16
Hosts =      2^12 - 2 = 4094 ( 4 bits in 3rd octet and 4th bits in 8 octet)

valid subnets = 256-240=16. 

Block Size =  0 ,16,3248, 64,80, 96,112, 128,144, 160,176 ,192,208 ,224,240   

NETWORK 1

172.16.0.0  (Network ID)
172.16.0.1  (First Host)
172.16.0.2
172.16.0.3
.
.
.
172.16.7.252
172.16.7.253
172.16.7.254 (Last Host)
172.16.7.255 (Broadcast ID)

MUST READ

when the address 0.255  after that 3rd octet will be started from 1.0 then 1.1, 1.2, 1.3 similarly address reach 1.255  3rd octet will start From  2.0  Similarly  all the address will allocate in a same way. ( For Understanding the Procedure)

NETWORK  2

172.16.8.0  (Network ID)
172.16.8.1  (First Host)
172.16.8.2
172.16.8.3
.
.
.
172.16.15.252
172.16.15.253
172.16.15.254  (Last Host)
172.16.15.255  (Broadcast ID)

NETWORK  3

172.16.16.0  (Network ID)
172.16.16.1  (First Host)
172.16.16.2
172.16.16.3
.
.
.
172.16.23.252
172.16.23.253
172.16.23.254  (Last Host)
172.16.23.255  (Broadcast ID)

NETWORK  4

172.16.24.0  (Network ID)
172.16.24.1  (First Host)
172.16.24.2
172.16.24.3
.
.
.
172.16.31.252
172.16.31.253
172.16.31.254  (Last Host)

172.16.31.255  (Broadcast ID)

NETWORK  5

172.16.32.0  (Network ID)
172.16.32.1  (First Host)
172.16.32.2
172.16.32.3
.
.
.
172.16.39.252
172.16.39.253
172.16.39.254  (Last Host)

172.16.39.255  (Broadcast ID)

NETWORK  6

172.16.40.0  (Network ID)
172.16.40.1  (First Host)
172.16.40.2
172.16.40.3
.
.
.
172.16.47.252
172.16.47.253
172.16.47.254  (Last Host)

172.16.47.255  (Broadcast ID)

NETWORK  7

172.16.48.0  (Network ID)
172.16.48.1  (First Host)
172.16.48.2
172.16.48.3
.
.
.
172.16.55.252
172.16.55.253
172.16.55.254  (Last Host)

172.16.55.255  (Broadcast ID)

NETWORK  8

172.16.56.0  (Network ID)
172.16.56.1  (First Host)
172.16.56.2
172.16.56.3
.
.
.
172.16.63.252
172.16.63.253
172.16.63.254  (Last Host)

172.16.63.255  (Broadcast ID)

NETWORK  9

172.16.64.0  (Network ID)
172.16.64.1  (First Host)
172.16.64.2
172.16.64.3
.
.
.
172.16.71.252
172.16.71.253
172.16.71.254  (Last Host)

172.16.71.255  (Broadcast ID)

NETWORK  10

172.16.72.0  (Network ID)
172.16.72.1  (First Host)
172.16.72.2
172.16.72.3
.
.
.
172.16.739.252
172.16.79.253
172.16.79.254  (Last Host)

172.16.79.255  (Broadcast ID)

NETWORK  11

172.16.80.0  (Network ID)
172.16.80.1  (First Host)
172.16.80.2
172.16.80.3
.
.
.
172.16.87.252
172.16.87.253
172.16.87.254  (Last Host)

172.16.87.255  (Broadcast ID)

NETWORK  12

172.16.88.0  (Network ID)
172.16.88.1  (First Host)
172.16.88.2
172.16.88.3
.
.
.
172.16.95.252
172.16.95.253
172.16.95.254  (Last Host)

172.16.95.255  (Broadcast ID)

NETWORK  13

172.16.96.0  (Network ID)
172.16.96.1  (First Host)
172.16.96.2
172.16.96.3
.
.
.
172.16.103.252
172.16.103.253
172.16.103.254  (Last Host)

172.16.103.255  (Broadcast ID)

NETWORK  14

172.16.104.0  (Network ID)
172.16.104.1  (First Host)
172.16.104.2
172.16.104.3
.
.
.
172.16.111.252
172.16.111.253
172.16.111.254  (Last Host)

172.16.111.255  (Broadcast ID)

NETWORK  15

172.16.112.0  (Network ID)
172.16.112.1  (First Host)
172.16.112.2
172.16.112.3
.
.
.
172.16.119.252
172.16.119.253
172.16.119.254  (Last Host)

172.16.119.255  (Broadcast ID)

NETWORK  16

172.16.120.0  (Network ID)
172.16.120.1  (First Host)
172.16.120.2
172.16.120.3
.
.
.
172.16.127.252
172.16.127.253
172.16.127.254  (Last Host)

172.16.127.255  (Broadcast ID)

Subnetting Class B Address Problem 3

Google+

Must Remind (Keep in Mind)

128 |  1 0 0 0 0 0 0 0   (i.e. 1 Bit ON and 7 OFF)

192 |  1 1 0 0 0 0 0 0   (i.e. 2 Bits ON and 6 OFF)

224 |  1 1 1 0 0 0 0 0    (i.e. 3 Bits ON and 5 OFF)

240 |  1 1 1 1 0 0 0 0    (i.e. 4 Bits ON and 4 OFF)

248 |  1 1 1 1 1 0 0 0    (i.e. 5 Bits ON and 3 OFF)

252 |  1 1 1 1 1 1 0 0    (i.e. 6 Bits ON and 2 OFF)

254 |  1 1 1 1 1 1 1 0    (i.e. 7 Bits ON and 1 OFF)

255 |  1 1 1 1 1 1 1 1    (i.e. 8 Bits ON and  0 OFF)

PROBLEM  3.

172.16.0.0 (Network Address)
255.255.224.0 (/19)

Network = 2^3 = 8
Hosts =      2^13 - 2 = 8190 ( 5 bits in 3rd octet and 8 bits in 4th octet)

valid subnets = 256-224=32. 

Block Size =  0 ,32, 64, 96, 128, 160, 192, 224   

NETWORK 1

172.16.0.0  (Network ID)
172.16.0.1  (First Host)
172.16.0.2
172.16.0.3
.
.
.
172.16.31.252
172.16.31.253
172.16.31254 (Last Host)
172.16.31.255 (Broadcast ID)

MUST READ

when the address 0.255  after that 3rd octet will be started from 1.0 then 1.1, 1.2, 1.3 similarly address reach 1.255  3rd octet will start From  2.0  Similarly  all the address will allocate in a same way. ( For Understanding the Procedure)

NETWORK  2

172.16.32.0  (Network ID)
172.16.32.1  (First Host)
172.16.32.2
172.16.32.3
.
.
.
172.16.63.252
172.16.63.253
172.16.63.254  (Last Host)
172.16.63.255  (Broadcast ID)

NETWORK  3

172.16.64.0  (Network ID)
172.16.64.1  (First Host)
172.16.64.2
172.16.64.3
.
.
.
172.16.95.252
172.16.95.253
172.16.95.254  (Last Host)
172.16.95.255  (Broadcast ID)

NETWORK  4

172.16.96.0  (Network ID)
172.16.96.1  (First Host)
172.16.96.2
172.16.96.3
.
.
.
172.16.127.252
172.16.127.253
172.16.127.254  (Last Host)

172.16.127.255  (Broadcast ID)

NETWORK  5

172.16.128.0  (Network ID)
172.16.128.1  (First Host)
172.16.128.2
172.16.128.3
.
.
.
172.16.159.252
172.16.159.253
172.16.159.254  (Last Host)

172.16.159.255  (Broadcast ID)

NETWORK  6

172.16.160.0  (Network ID)
172.16.160.1  (First Host)
172.16.160.2
172.16.160.3
.
.
.
172.16.191.252
172.16.191.253
172.16.191.254  (Last Host)

172.16.191.255  (Broadcast ID)

NETWORK  7

172.16.192.0  (Network ID)
172.16.192.1  (First Host)
172.16.192.2
172.16.192.3
.
.
.
172.16.223.252
172.16.223.253
172.16.223.254  (Last Host)

172.16.223.255  (Broadcast ID)

NETWORK  8

172.16.224.0  (Network ID)
172.16.224.1  (First Host)
172.16.224.2
172.16.224.3
.
.
.
172.16.255.252
172.16.255.253
172.16.255.254  (Last Host)

172.16.255.255  (Broadcast ID)

Subnetting Class B Address Problem 2

Must Remind (Keep in Mind)

128 |  1 0 0 0 0 0 0 0   (i.e. 1 Bit ON and 7 OFF)

192 |  1 1 0 0 0 0 0 0   (i.e. 2 Bits ON and 6 OFF)

224 |  1 1 1 0 0 0 0 0    (i.e. 3 Bits ON and 5 OFF)

240 |  1 1 1 1 0 0 0 0    (i.e. 4 Bits ON and 4 OFF)

248 |  1 1 1 1 1 0 0 0    (i.e. 5 Bits ON and 3 OFF)

252 |  1 1 1 1 1 1 0 0    (i.e. 6 Bits ON and 2 OFF)

254 |  1 1 1 1 1 1 1 0    (i.e. 7 Bits ON and 1 OFF)

255 |  1 1 1 1 1 1 1 1    (i.e. 8 Bits ON and  0 OFF)

PROBLEM  2.

172.16.0.0 (Network Address)
255.255.192.0 (/18)

Network = 2^2 = 4
Hosts =      2^14 - 2 = 16382 ( 6 bits in 3rd octet and 8 bits in 4th octet)

valid subnets = 256-192=64. 

Block Size =  0 , 64, 128   

That subetting is performing  in the third octet , So subnet are really 0.0 , 64.0 , 128.0 ,192.0 

NETWORK 1

172.16.0.0  (Network ID)
172.16.0.1  (First Host)
172.16.0.2
172.16.0.3
.
.
.
172.16.63.252
172.16.63.253
172.16.63.254 (Last Host)
172.16.63.255 (Broadcast ID)

MUST READ

when the address 0.255  after that 3rd octet will be started from 1.0 then 1.1, 1.2, 1.3 similarly address reach 1.255  3rd octet will start From  2.0  Similarly  all the address will allocate in a same way. ( For Understanding the Procedure)

NETWORK  2

172.16.64.0  (Network ID)
172.16.64.1  (First Host)
172.16.64.2
172.16.64.3
.
.
.
172.16.127.252
172.16.127.253
172.16.127.254  (Last Host)
172.16.127.255  (Broadcast ID)

NETWORK  3

172.16.128.0  (Network ID)
172.16.128.1  (First Host)
172.16.128.2
172.16.128.3
.
.
.
172.16.191.252
172.16.191.253
172.16.191.254  (Last Host)
172.16.191.255  (Broadcast ID)

NETWORK  4

172.16.192.0  (Network ID)
172.16.192.1  (First Host)
172.16.192.2
172.16.192.3
.
.
.
172.16.255.252
172.16.255.253
172.16.255.254  (Last Host)
172.16.255.255  (Broadcast ID)

Subnetting Class B Address Problem 1

Must Remind (Keep in Mind)

128 |  1 0 0 0 0 0 0 0   (i.e. 1 Bit ON and 7 OFF)

192 |  1 1 0 0 0 0 0 0   (i.e. 2 Bits ON and 6 OFF)

224 |  1 1 1 0 0 0 0 0    (i.e. 3 Bits ON and 5 OFF)

240 |  1 1 1 1 0 0 0 0    (i.e. 4 Bits ON and 4 OFF)

248 |  1 1 1 1 1 0 0 0    (i.e. 5 Bits ON and 3 OFF)

252 |  1 1 1 1 1 1 0 0    (i.e. 6 Bits ON and 2 OFF)

254 |  1 1 1 1 1 1 1 0    (i.e. 7 Bits ON and 1 OFF)

255 |  1 1 1 1 1 1 1 1    (i.e. 8 Bits ON and  0 OFF)

PROBLEM  1.

172.16.0.0 (Network Address)
255.255.128.0 (/17)

Network = 2^1 = 2
Hosts =      2^15 - 2 = 32766 ( 7 bits in 3rd octet and 8 bits in 4th octet)

valid subnets = 256-128=128. 

Block Size =  0 , 128   

That subetting is performing  in the tird octet , So subnet are really 0.0 and  128.0  These are the exact numbers we used with Class C we used that in the 3rd Octet then add 0 in the 4th Octet for the network address. (MUST READ)

Network1

172.16.0.0  (Network ID)
172.16.0.1
172.16.0.2
172.16.0.3
.
.
.
172.16.127.252
172.16.127.253
172.16.127.254
172.16.127.255 (Broadcast ID)

when the address 0.255  after that 3rd octet will be started from 1.0 then 1.1, 1.2, 1.3 similarly address reach 1.255  3rd octet will start From  2.0  Similarly  all the address will allocate in a same way. (MUST READ)

NETWORK  2


172.16.128.0  (Network ID)
172.16.128.1
172.16.128.2
172.16.128.3
.
.
.
172.16.255.252
172.16.255.253
172.16.255.254
172.16.255.255  (Broadcast ID)