IP Addressing Practice 1
A. Identifying Network Addresses
Using the IP address and subnet mask shown write out the network address:
188.10.18.2
255.255.0.0 _____________________________
10.10.48.80
255.255.255.0 _____________________________
192.149.24.191
255.255.255.0 _____________________________
150.203.23.19
255.255.0.0 _____________________________
10.10.10.10
255.0.0.0 _____________________________
186.13.23.110
255.255.255.0 _____________________________
223.69.230.250
255.255.0.0 _____________________________
200.120.135.15
255.255.255.0 _____________________________
27.125.200.151
255.0.0.0 _____________________________
199.20.150.35
255.255.255.0 _____________________________
191.55.165.135
255.255.255.0 _____________________________
28.212.250.254
255.255.0.0 _____________________________
B. Identifying the Host Addresses
Using the IP address and subnet mask shown, circle the host address portion:
188.10.18.2 255.255.0.0
10.10.48.80 255.255.255.0
222.49.49.11 255.255.255.0
128.23.230.19 255.255.0.0
10.10.10.10 255.0.0.0
200.113.123.11 255.255.255.0
223.169.23.20 255.255.0.0
203.20.35.215 255.255.255.0
117.15.2.51 255.0.0.0
199.120.15.135 255.255.255.0
191.55.165.135 255.255.255.0
48.21.25.54 255.255.0.0
C. Problems Solving
1. What is the number of bits in an IPv4 address? What is the number of bits in an IPv6
address?
2. What is NAT? How can NAT help in address depletion?
3. What is the address space in a system with 8 bit, 16 bit and 64 bit addresses?
4. Find the network address of the following IP addresses
a. 192.168.10.50/24
b. 192.168.100.20/26
c. 192.168.50.250/28
d. 10.10.10.1/8
e. 10.10.50.102/10
f. 138.80.50.10/16
g. 138.80.44.197/20
How to determine the number of subnets and the number of hosts per subnet
Two formulas can provide this basic information:
Number of subnets = 2s
Number of hosts per subnet = 2h - 2
Both formulas calculate the number of hosts or subnets based on the number of binary bits
used. For example if you borrow three bits from the host portion of the address use the
number of subnets formula to determine the total number of subnets gained by borrowing the
three bits. This would be 23 or 2 x 2 x 2 = 8 subnets
To determine the number of hosts per subnet you would take the number of binary bits used
in the host portion and apply this to the number of hosts per subnet formula If five bits are in
the host portion of the address this would be 25 or 2 x 2 x 2 x 2 x 2 = 32 hosts.
When dealing with the number of hosts per subnet you have to subtract two addresses from
the range. The first address in every range is the subnet number. The last address in every
range is the broadcast address. These two addresses cannot be assigned to any device in the
network which is why you have to subtract two addresses to find the number of usable
addresses in each range.
For example if two bits are borrowed for the network portion of the address you can easily
determine the number of subnets and hosts per subnets using the two formulas.
D. Subnetting Exercises
1. Fill in the table below:
Prefix Decimal Mask Total Hosts Usable Hosts
/24
255.255.255.252
1,024
62
8
255.255.0.0
/21
30
/25
255.255.224.0
2. You’ve been given a block of IP addresses as defined by the mask in the first
column. You decide to subdivide that block into multiple smaller blocks as
defined by the mask in the second column. Fill in the table with the missing
information. You can use all subnets (subnet zero is not reserved.)
Mask Given Mask Giving Out # of Subnets Usable Hosts Each
/24 /27
/24 255.255.255.252
/15 1,024
255.255.240.0 62
8 126
255.255.0.0 256
/21 64
255.255.254.0 30
/25 255.255.255.248
255.255.252.0 2
