> | Lab 10.7.7 Subnet Mask Estimated time: 45 min. Objectives: This Lab will focus on your ability to accomplish the following tasks: Work with a more complex Class C subnet scenario Determine the subnets available with a particular IP Network address and Subnet mask Given a network address and requirements for how many subnets and hosts, be able to determine what subnet mask should be used Given a network address and a subnet mask, be able to determine the number of subnets and hosts per subnet that can be created as well as useable subnets and useable number of hosts Assign IP addresses and subnet masks to hosts and router interfaces Use the "ANDing" process to move an IP packet from a local host to a remote host through a router Background: This lab will build on Lab Subnet Mask 1 and help develop a better understanding of IP subnet masks using a real-world example with additional worksheet exercises based on foundations established in the prior lab. This lab will focus on a Class C network with three subnets and using a Custom Subnet Mask . Tools / Preparation: This is primarily a written lab exercise but you will want to use Control Panel / Network to review some real network IP addresses and the basics covered in the prior lab. The following resources will be required: PC workstation with Windows operating system (Win 95, 98, NT or 2000) installed on the PC and access to the Windows Calculator. Notes: Step 1 – IP Address Basics Explanation: For reference, the IP addressing table from the prior lab is included here. IP network addresses are assigned by the Internet Network Information Center (InterNIC). You will work with a Class C.
> Adr Cls | 1st Octet Decimal Range | 1st Octet High Order Bits | Network / Host ID (N=Network, H=Host) | Default Subnet Mask | Number of Networks | Hosts per Network (usable addresses)
> A | 1 – 126* | 0 | N.H.H.H | 255.0.0.0 | 126 (27 – 2) | 16,777,214 (2 24 – 2)
> B | 128 – 191 | 1 0 | N.N.H.H | 255.255.0.0 | 16,382 (214 - 2) | 65,534 (2 16 – 2)
> C | 192 – 223 | 1 1 0 | N.N.N.H | 255.255.255.0 | 2,097,150 (221 – 2) | 254 (2 8 – 2)
> D | 224 – 239 | 1 1 1 0 | Reserved for Multicasting
> E | 240 – 254 | 1 1 1 1 0 | Experimental, used for research
Step 2 – Class C network address with 3 subnets. Task: Use the following information and use the information from the worksheet in the prior lab to help determine your valid subnets and host IP addresses. Do NOT use the zero or last subnet. Explanation: Your company has a class C network address of 200.10.57.0. You want to subdivide your physical network into 3 subnets (A, B and C) using a router as shown in the diagram at the end of the worksheet. You will need at least 20 hosts per subnet. Answer the following questions. What is the binary equivalent of the Class C network address 200.10.57.0 in the exercise? ___________ . _____________ . _____________ . ______________ Which octet(s) represent the network portion and which octet(s) represent the host portion of this Class C network address? _______________________________ How many bits must you borrow from the host portion of the network address in order to provide at least 3 subnets and at least 20 hosts per subnet? _______________________________ What will the Subnet Mast be (using dotted decimal notation) based on the number of bits borrowed in step 3? _____________ . _____________ . ______________ . ______________ What is the binary equivalent of the subnet mask above: _____________ . _____________ . ______________ . ______________ Step 3 – Class C network address with 3 subnets. Task: Use the diagram below to fill in the blanks and answer the following questions. Explanation: Be sure to specify all four octets for subnet address and subnet mask. The same subnet mask should be used for all hosts, router interfaces and all subnets. Having a common subnet mask will allow hosts and routers to determine which subnet the IP packet is intended for. Router interfaces will usually be numbered first when assigning IP addresses and hosts will receive higher numbers. Fill in the following table for each of the possible subnets that can be created by borrowing 3 bits for subnets from the fourth octet (host octet). Identify the Network Address, the Subnet Mask, the Subnetwork Address, the range of possible host IP addresses for each subnet, the broadcast address of each subnet and also indicate whether the subnet is useable or not. You will only use 3 of these subnets for the exercise.
SN# | Network Address | Subnet mask | Subnetwork Address | Range of possible Host IP Addresses | Broadcast Address | Use?
0 |  |  |  |  |  |
1 |  |  |  |  |  |
2 |  |  |  |  |  |
3 |  |  |  |  |  |
4 |  |  |  |  |  |
5 |  |  |  |  |  |
6 |  |  |  |  |  |
7 |  |  |  |  |  |
Assign an IP Address and Subnet Mask to router interface A and write it down here. __________________ / ___________________ Assign an IP Address and Subnet Mask of router interface B and write it down here. __________________ / ___________________ Assign an IP Address and Subnet Mask of router interface C and write it down here. __________________ / ___________________ Assign a host IP Address to Host X on Subnet A and assign an IP address to Host Z on Subnet C (answers may vary). Describe the steps (using ANDing) for the process of sending an IP packet from Host X to host Z through the router. Remember, when ANDing, two 1s together the result is a 1, ANDing any other combination (1 and 0, 0 and 1 or 0 and 0) results in a Zero (0). Also, when ANDing two network IP addresses together the result of the ANDing process will be the network (or subnetwork) address of the destination IP address in the packet. Use the information from the diagram above and prior lab to help assign IP addresses and subnet masks. What is the result of the ANDing process for Host X? Decimal Host X IP addr: _________ . _________ . ___________ . ____________ Binary Host X IP addr: _________ . _________ . ___________ . ____________ Binary Subnet Mask: _________ . _________ . ___________ . ____________ Binary ANDing Result: _________ . _________ . ___________ . ____________ Decimal ANDing Result: _________ . _________ . ___________ . ____________ What is the result of the ANDing process for Host Z? Decimal Host Z IP addr: _________ . _________ . ___________ . ____________ Binary Host Z IP addr: _________ . _________ . ___________ . ____________ Binary Subnet Mask: _________ . _________ . ___________ . ____________ Binary ANDing Result: _________ . _________ . ___________ . ____________ Decimal ANDing Result: _________ . _________ . ___________ . ____________ The Decimal ANDing result from questions 7 is the network/subnet that Host X is on. The result from question 8 is the network/subnet that Host Z is on. Are Host X and Host Z on the same network/subnet? ______________ What will Host X now do with the packet ? __________________________________________ _________________________________________________________________________________ Fill in the blanks in the following diagram with the correct Network and IP addresses.