Student Name: ___________________________
CHABOT COLLEGE
CISCO NETWORKING ACADEMY I
10A - SUBNET CONCEPTS
Directions: Write the decimal value of each of the octets shown in the table below:
Bit
27
26
25
24
23
22
21
20
=
128
64
32
16
8
4
2
1
=
1
0
0
0
0
0
0
0
=
1
1
0
0
0
0
0
0
=
1
1
1
0
0
0
0
0
=
1
1
1
1
0
0
0
0
=
1
1
1
1
1
0
0
0
=
1
1
1
1
1
1
0
0
=
1
1
1
1
1
1
1
0
=
1
1
1
1
1
1
1
1
=
Decimal
Value
Directions: For each address and subnet mask pair:
 write the binary value of the subnet mask
 use the boolean ANDing process to determine the network number in binary and decimal.
The first one is done to get you started. Use chapter 10 as a reference.
Decimal
Host Address
194.100.10.35
Subnet Mask
255.255.255.240
ANDing Result SubNetwork No.
194.100.10.32
Binary
11000010
11111111
11000010
Decimal
Host Address
194.100.10.70
Subnet Mask
255.255.255.224
01100100 00001010 00100011
11111111 11111111 11110000
01100100 00001010 00100000
Binary
11000010
11111111
01100100 00001010 01000110
11111111 11111111
ANDing Result SubNetwork No.
Decimal
Host Address
194.100.10.129
Subnet Mask
255.255.255.240
Binary
11000010
11111111
ANDing Result SubNetwork No.
1
01100100 00001010 10000001
11111111 11111111
Student Name: ___________________________
Formulas to remember:
No. Usable Subnets Created = 2No. Borrowed Bits -2
(Remember to subtract 2 for the Network Address and Broadcast Address)
No. Usable Hosts/Subnet = 2No. Host Bits Remaining -2
(Remember to subtract 2 for the Subnetwork Address and Subnetwork Broadcast Address)
Fourth Octet Reference Table: (study)
Fourth Octet Bit Positions
7
6
5
4
3
2
1
0
Subnet No. Usable 2 2 2 2 2 2 2 2
Bits
Subnets 128 64 32 16 8 4 2 1
0
20 - 2 = 0 0 0 0 0 0 0 0 0
1
21 - 2 = 0 1 0 0 0 0 0 0 0
2
22 - 2 = 2 1 1 0 0 0 0 0 0
3
23 - 2 = 6 1 1 1 0 0 0 0 0
4
24 - 2 = 14 1 1 1 1 0 0 0 0
5
25 - 2 = 30 1 1 1 1 1 0 0 0
6
26 - 2 = 62 1 1 1 1 1 1 0 0
7
27 - 2 = 126 1 1 1 1 1 1 1 0
8
28 - 2 = 254 1 1 1 1 1 1 1 1
No. Usable
Hosts
254 = 28 - 2
126 = 27 - 2
62 = 26 - 2
30 = 25 - 2
14 = 24 - 2
6 = 23 - 2
2 = 22 - 2
0 = 21 - 2
0 = 20 - 2
Host
Bits
8
7
6
5
4
3
2
1
0
Directions: Complete the table below.
When finished, cross out any row that contains no usable subnets or no usable hosts:
Class C Subnet Masks
Subnet Mask
Subnet
Decimal
Bit
count
Binary
(4th Octet)
No. Bits
Borrowed
255.255.255.0
/24
00000000
0 (default)
255.255.255.128
/25
10000000
1
255.255.255.192
/26
11000000
2
255.255.255.224
/27
11100000
3
255.255.255.240
/28
11110000
4
255.255.255.248
/29
11111000
5
255.255.255.252
/30
11111100
6
255.255.255.254
/31
11111110
7
255.255.255.255
/32
11111111
8
2
No.
Subnets
Host
No.
Usable
No.
Bits
No.
No.
Hosts
Usable
(/subnet) (/subnet)
Student Name: ___________________________
Directions: Complete the table below.
Usable Class C Subnets
Subnet Mask
Bitcount
No.
Usable
Subnets
Decimal
No. Usable
Hosts/
Subnet
(all 4 Octets)
/26
/27
/28
/29
/30
Directions: Answer the following questions:
1.
What address class has a default subnet mask of /8? _________
2.
Write the subnet mask /16 in dotted decimal format: __________________________
3.
How many host bits are specified by the subnet mask /8? ____________
4.
How many host bits are specified by the subnet mask /24? ____________
5.
How many host bits are specified by the subnet mask /28? ____________
6.
How many host bits are specified by the subnet mask /30? ____________
7.
With a /30 mask, how many host addresses (including unusable ones) will be in each subnet? _________
Examine the following table...
8.
How much is the increment (the increase) between starting addresses of each of the subnets? _______
9.
Complete the last 3 rows of the table:
Subnet
Address Range (4th Octet)
Subnet 0
0-3
Subnet 1
4-7
Subnet 2
8 - 11
Subnet 3
12 - 15
Subnet 4
16 - 19
Subnet 5
Subnet 6
Subnet 7
Etc… to 64
subnets
(Stop here…)
/
10. What subnet mask fits this table?
.
END | THREE-HOLE PUNCH | STAPLE | SUBMIT
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