# Appendix Lab – Subnetting Network Topologies Answers

## Lab – Subnetting Network Topologies (Answers Version)

Answers 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.
• Assign addresses and subnet mask pairs to device interfaces.
• 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.

1. How many subnets are there? ___________ 2
2. How many bits should you borrow to create the required number of subnets? _________ 1
3. How many usable host addresses per subnet are in this addressing scheme? ___________ 126
4. What is the new subnet mask in dotted decimal format? _________________________ 255.255.255.128
5. How many subnets are available for future use? _______________ 0

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

Fill in the following table with the subnet information:

 Subnet Number Subnet Address First Usable Host Address Last Usable Host Address Broadcast Address 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.

1. How many subnets are there? ___________ 4
2. How many bits should you borrow to create the required number of subnets? _________ 2
3. How many usable host addresses per subnet are in this addressing scheme? ___________ 62
4. What is the new subnet mask in dotted decimal format? _________________________ 255.255.255.192
5. How many subnets are available for future use? _______________ 0

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

Fill in the following table with the subnet information:

 Subnet Number Subnet Address First Usable Host Address Last Usable Host Address Broadcast Address 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.

1. How many subnets are there? ___________ 6
2. How many bits should you borrow to create the required number of subnets? _________ 3
3. How many usable host addresses per subnet are in this addressing scheme? ___________ 30
4. What is the new subnet mask in dotted decimal format? _________________________ 255.255.255.224
5. How many subnets are available for future use? _______________ 2

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

Fill in the following table with the subnet information:

 Subnet Number Subnet Address First Usable Host Address Last Usable Host Address Broadcast Address 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.

1. Fill in the following table with IP addresses and subnet masks for the router interfaces:
Answers Note: These are suggested IP addresses based on using the first 6 subnets from the table above as assigned to each segment.

 Device Interface IP Address Subnet Mask 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
2. Fill in the following table with the IP addresses and subnet masks for devices in the LAN as displayed in topology.
Answers Note: These are suggested IP addresses based on using the first 6 subnets from the table above as assigned to each segment.

 Device Interface IP Address Subnet Mask Default Gateway 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.

1. How many subnets are there? ___________ 9
2. How many bits should you borrow to create the required number of subnets? _________ 4
3. How many usable host addresses per subnet are in this addressing scheme? ___________ 14
4. What is the new subnet mask in dotted decimal format? _________________________ 255.255.255.240
5. How many subnets are available for future use? _______________ 7

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

Fill in the following table with the subnet information.

 Subnet Number Subnet Address First Usable Host Address Last Usable Host Address Broadcast Address 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.

1. How many subnets are there? ___________ 9
2. How many bits should you borrow to create the required number of subnets? _________ 4
3. How many usable host addresses per subnet are in this addressing scheme? ___________ 2046
4. What is the new subnet mask in dotted decimal format? _________________________ 255.255.248.0
5. How many subnets are available for future use? _______________ 7

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

Fill in the following table with the subnet information:

 Subnet Number Subnet Address First Usable Host Address Last Usable Host Address Broadcast Address 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.

1. Fill in the following table with IP addresses and subnet masks for the router interfaces:
Answers Note: These are suggested IP addresses based on using the first 9 subnets from the table above as assigned to each segment.

 Device Interface IP Address Subnet Mask 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.