# Appendix Lab – Subnetting Network Topologies - Answers

### Lab – Subnetting Network Topologies (Instructor Version)

Instructor Note: Red font color or Gray highlights indicate text that appears in the instructor copy only.

### Objectives

Parts 1 to 5, for each network topology:

• Determine the number of subnets.
• Design an appropriate addressing scheme.
• Examine the use of the available network address space and future growth potential.

### Background / Scenario

When given a network topology, it is important to be able to determine the number of subnets required. In this lab, several scenario topologies will be provided, along with a base network address and mask. You will subnet the network address and provide an IP addressing scheme that will accommodate the number of subnets displayed in the topology diagram. You must determine the number of bits to borrow, the number of hosts per subnet, and potential for growth as specified by the instructions.

#### Part 1: Network Topology A

In Part 1, you have been given the 192.168.10.0/24 network address to subnet, with the following topology. Determine the number of networks needed and then design an appropriate addressing scheme.

##### Step 1: Determine the number of subnets in Network Topology A.

a. How many subnets are there? _____________
2

b. How many bits should you borrow to create the required number of subnets? _____________
1

c. How many usable host addresses per subnet are in this addressing scheme? _____________
126

d. What is the new subnet mask in dotted decimal format? _____________
255.255.255.128

e. How many subnets are available for future use? _____________
0

##### Step 2: Record the subnet information.

Fill in the following table with the subnet information:

0 192.168.10.0 192.168.10.1 192.168.10.126 192.168.10.127
1 192.168.10.128 192.168.10.129 192.168.10.254 192.168.10.255
2
3
4
5

#### Part 2: Network Topology B

The network topology from Part 1 has expanded to accommodate the addition of router R3 and its accompanying network, as illustrated in the following topology. Use the 192.168.10.0/24 network address to provide addresses to the network devices, and then design a new addressing scheme to support the additional network requirement.

##### Step 1: Determine the number of subnets in Network Topology B.

a. How many subnets are there? _____________
4

b. How many bits should you borrow to create the required number of subnets? _____________
2

c. How many usable host addresses per subnet are in this addressing scheme? _____________
62

d. What is the new subnet mask in dotted decimal format? _____________
255.255.255.192

e. How many subnets are available for future use? _____________
0

##### Step 2: Record the subnet information.

Fill in the following table with the subnet information:

0 192.168.10.0 192.168.10.1 192.168.10.62 192.168.10.63
1 192.168.10.64 192.168.10.65 192.168.10.126 192.168.10.127
2 192.168.10.128 192.168.10.129 192.168.10.190 192.168.10.191
3 192.168.10.192 192.168.10.193 192.168.10.254 192.168.10.255
4
5
6
7

#### Part 3: Network Topology C

The topology has changed again with a new LAN added to R2 and a redundant link between R1 and R3. Use the 192.168.10.0/24 network address to provide addresses to the network devices. Also provide an IP address scheme that will accommodate these additional devices. For this topology, assign a subnet to each network.

##### Step 1: Determine the number of subnets in Network Topology C.

a. How many subnets are there? _____________
6

b. How many bits should you borrow to create the required number of subnets? _____________
3

c. How many usable host addresses per subnet are in this addressing scheme? _____________
30

d. What is the new subnet mask in dotted decimal format? _____________
255.255.255.224

e. How many subnets are available for future use? _____________
2

##### Step 2: Record the subnet information.

Fill in the following table with the subnet information:

0 192.168.10.0 192.168.10.1 192.168.10.30 192.168.10.31
1 192.168.10.32 192.168.10.33 192.168.10.62 192.168.10.63
2 192.168.10.64 192.168.10.65 192.168.10.94 192.168.10.95
3 192.168.10.96 192.168.10.97 192.168.10.126 192.168.10.127
4 192.168.10.128 192.168.10.129 192.168.10.158 192.168.10.159
5 192.168.10.160 192.168.10.161 192.168.10.190 192.168.10.191
6 192.168.10.192 192.168.10.193 192.168.10.222 192.168.10.223
7 192.168.10.224 192.168.10.225 192.168.10.254 192.168.10.255
8
9
10
##### Step 3: Assign addresses to network devices in the subnets.

a. Fill in the following table with IP addresses and subnet masks for the router interfaces:

Instructor Note: These are suggested IP addresses based on using the first 6 subnets from the table above as assigned to each segment.

R1 GigabitEthernet 0/1 192.168.10.1 255.255.255.224
Serial 0/0/0 192.168.10.33 255.255.255.224
Serial 0/0/1 192.168.10.65 255.255.255.224
R2 GigabitEthernet 0/1 192.168.10.97 255.255.255.224
Serial 0/0/0 192.168.10.34 255.255.255.224
Serial 0/0/1 192.168.10.129 255.255.255.224
R3 GigabitEthernet 0/1 192.168.10.161 255.255.255.224
Serial 0/0/0 192.168.10.66 255.255.255.224
Serial 0/0/1 192.168.10.130 255.255.255.224

b. Fill in the following table with the IP addresses and subnet masks for devices in the LAN as displayed in topology.

Instructor Note: These are suggested IP addresses based on using the first 6 subnets from the table above as assigned to each segment.

PC-A NIC 192.168.10.30 255.255.255.224 192.168.10.1
PC-B NIC 192.168.10.29 255.255.255.224 192.168.10.1
S1 VLAN 1 192.168.10.2 255.255.255.224 192.168.10.1
PC-C NIC 192.168.10.126 255.255.255.224 192.168.10.97
PC-D NIC 192.168.10.125 255.255.255.224 192.168.10.97
S2 VLAN 1 192.168.10.98 255.255.255.224 192.168.10.97
PC-E NIC 192.168.10.190 255.255.255.224 192.168.10.161
PC-F NIC 192.168.10.189 255.255.255.224 192.168.10.161
S3 VLAN 1 192.168.10.162 255.255.255.224 192.168.10.161

#### Part 4: Network Topology D

The network was modified to accommodate changes in the organization. The 192.168.10.0/24 network address is used to provide the addresses in the network.

##### Step 1: Determine the number of subnets in Network Topology D.

a. How many subnets are there? _____________
9

b. How many bits should you borrow to create the required number of subnets? _____________
4

c. How many usable host addresses per subnet are in this addressing scheme? _____________
14

d. What is the new subnet mask in dotted decimal format? _____________
255.255.255.240

e. How many subnets are available for future use? _____________
7

##### Step 2: Record the subnet information.

Fill in the following table with the subnet information.

0 192.168.10.0 192.168.10.1 192.168.10.14 192.168.10.15
1 192.168.10.16 192.168.10.17 192.168.10.30 192.168.10.31
2 192.168.10.32 192.168.10.33 192.168.10.46 192.168.10.47
3 192.168.10.48 192.168.10.49 192.168.10.62 192.168.10.63
4 192.168.10.64 192.168.10.65 192.168.10.78 192.168.10.79
5 192.168.10.80 192.168.10.81 192.168.10.94 192.168.10.95
6 192.168.10.96 192.168.10.97 192.168.10.110 192.168.10.111
7 192.168.10.112 192.168.10.111 192.168.10.126 192.168.10.127
8 192.168.10.128 192.168.10.129 192.168.10.142 192.168.10.143
9 192.168.10.144 192.168.10.145 192.168.10.158 192.168.10.159
10 192.168.10.160 192.168.10.161 192.168.10.174 192.168.10.175
11 192.168.10.176 192.168.10.177 192.168.10.190 192.168.10.191
12 192.168.10.192 192.168.10.193 192.168.10.206 192.168.10.207
13 192.168.10.208 192.168.10.209 192.168.10.222 192.168.10.223
14 192.168.10.224 192.168.10.225 192.168.10.238 192.168.10.239
15 192.168.10.240 192.168.10.241 192.168.10.254 192.168.10.255
16
17

#### Part 5: Network Topology E

The organization has a network address of 172.16.128.0/17 to be divided as illustrated in the following topology. You must choose an addressing scheme that can accommodate the number of networks and hosts in the topology.

##### Step 1: Determine the number of subnets in Network Topology E.

a. How many subnets are there? _____________
9

b. How many bits should you borrow to create the required number of subnets? _____________
4

c. How many usable host addresses per subnet are in this addressing scheme? _____________
2046

d. What is the new subnet mask in dotted decimal format? _____________
255.255.248.0

e. How many subnets are available for future use? _____________
7

##### Step 2: Record the subnet information.

Fill in the following table with the subnet information:

0 172.16.128.0 172.16.128.1 172.16.135.254 172.16.135.255
1 172.16.136.0 172.16.136.1 172.16.143.254 172.16.143.255
2 172.16.144.0 172.16.144.1 172.16.151.254 172.16.151.255
3 172.16.152.0 172.16.152.1 172.16.159.254 172.16.159.255
4 172.16.160.0 172.16.160.1 172.16.167.254 172.16.167.255
5 172.16.168.0 172.16.168.1 172.16.175.254 172.16.175.255
6 172.16.176.0 172.16.176.1 172.16.183.254 172.16.183.255
7 172.16.184.0 172.16.184.1 172.16.191.254 172.16.191.255
8 172.16.192.0 172.16.192.1 172.16.199.254 172.16.199.255
9 172.16.200.0 172.16.200.1 172.16.207.254 172.16.207.255
10 172.16.208.0 172.16.208.1 172.16.215.254 172.16.215.255
11 172.16.216.0 172.16.216.1 172.16.223.254 172.16.223.255
12 172.16.224.0 172.16.224.1 172.16.231.254 172.16.231.255
13 172.16.232.0 172.16.232.1 172.16.239.254 172.16.239.255
14 172.16.240.0 172.16.240.1 172.16.247.254 172.16.247.255
15 172.16.248.0 172.16.248.1 172.16.255.254 172.16.255.255
16
17
##### Step 3: Assign addresses to network devices in the subnets.

a. Fill in the following table with IP addresses and subnet masks for the router interfaces:

Instructor Note: These are suggested IP addresses based on using the first 9 subnets from the table above as assigned to each segment.

R1 GigabitEthernet 0/0 172.16.128.1 255.255.248.0
GigabitEthernet 0/1 172.16.136.1 255.255.248.0
Serial 0/0/0 172.16.144.1 255.255.248.0
Serial 0/0/1 172.16.152.1 255.255.248.0
R2 GigabitEthernet 0/0 172.16.160.1 255.255.248.0
GigabitEthernet 0/1 172.16.168.1 255.255.248.0
Serial 0/0/0 172.16.144.2 255.255.248.0
Serial 0/0/1 172.16.176.1 255.255.248.0
R3 GigabitEthernet 0/0 172.16.184.1 255.255.248.0
GigabitEthernet 0/1 172.16.192.1 255.255.248.0
Serial 0/0/0 172.16.152.2 255.255.248.0
Serial 0/0/1 172.16.176.2 255.255.248.0

### Reflection

1. What information is needed when determining an appropriate addressing scheme for a network? _____________
Number of networks and hosts are needed when determining an appropriate addressing scheme for a network.
2. After the subnets are assigned, will all the host addresses be utilized in each subnet? _____________
No. For the WAN serial links, only two addresses will be utilized. For the subnets with host PCs, all the addresses can be used in each subnet.