Chapter 4 Planning and Addressing Structure

Lab 4.1.5 Subnetting a Network

Step 1: Analyze the network

a. Referring to the Rough Design Notes, determine the minimum number of hosts that a subnet needs
to support the new network design.
1) The largest subnet must be able to support 3 hosts.
2) To support that many hosts, the number of host bits required is? (6)

b. What is the minimum number of subnets required for the new network design? (32)

c. Can this network be subnetted according to the requirements?
For example: If four subnets are required and the largest subnet has to support 128 hosts, this is a
problem, because a subnet in a class C network that has been partitioned four ways can support only
62 hosts.

d. Fill in the blanks to summarize the subnetting requirements of this new network design:
This network requires    subnets, each supporting 29 hosts. Therefore, 6 host ID
bits are reserved for the subnet ID. With those values, this network supports 32 subnets, each
subnet having 6 hosts.

Step 2: Calculate the custom subnet mask

Now that the number of subnet ID bits is known, the subnet mask can be calculated. A class C network has a
default subnet mask of 24 bits, or What will the custom subnet mask be?
The custom subnet mask for this network will be _____._____._____._____, or /_____.

Step 3: Specify the host IP addresses

Now that the subnet mask is identified, the network addressing scheme can be created. The addressing scheme includes the subnet number, the subnet broadcast address, and the range of IP addresses
assignable to hosts.

a. Complete the table showing all the possible subnets for the network.

b. for it to be completed. Hosts will be assigned IP addresses as follows: (fill in the table below)

Step 4: Consider other subnetting options

What if there were more than 30 hosts that needed to be supported on either the wired or wireless portion of
the network. You could borrow fewer bits, which would create fewer subnets, but each one would support a
greater number of hosts per subnet.

a. How many bits would be borrowed to create four subnets? 1

b. How many bits would be left for hosts on each subnet? 7

c. What is the maximum number of hosts each subnet could support? 128

d. What would the subnet mask be in dotted decimal and slash number (/#) format? / 11111111.11111111.11111111.00000000

e. If you start with the same network as before and subnet it into four subnets, what would
the subnet numbers be?

Step 5: Reflection

a. Does subnetting help reduce the problem of IP address depletion? Explain your answer.

ya, karena dengan subnetting dapatmengurangi network traffic sehingga dapat mengoptimalkan network performance.

b. The Rough Design Notes diagram noted that the wireless subnet would have up to 30 PCs connecting. In pairs or in small groups, discuss whether or not that creates a situation in which IP addresses might get wasted. Does it matter, and why or why not?

c. There are alternate methods of subnetting using CIDR and VLSM. Would VLSM be a worthwhile option for subnetting this network? Discuss in small groups.

Dengan VLSM proses subnetting dilakukan berdasarkan segmen jaringan yang dibutuhkan oleh jumlah host terbanyak. Subnetting diaplikasukan secara rekursif untuk membentuk beberapa subjaringan dengan ukuran bervariasi, yang diturunkan dari network identifier yang sama.

Lab 4.2.4 Determining PAT Translations

Step 1: Determine the IP address of the computer

a. Open a Command Prompt window by clicking Start > Run and typing cmd. Alternatively, you may click Start > All programs > Accessories > Command Prompt. At the prompt, type the ipconfig command to display the IP address of the computer.

b. What is the IP address of the computer? tidak ada alamat IP

c. Is there a port number shown, and why or why not?

Step 2: Determine the IP addresses of the gateway router or ISR

Check with your instructor to get the IP addresses for the ISR NAT router gateway.
Internal Ethernet address:
External Internet address:

Step 3: Display baseline netstat results

a. At the command prompt, type the netstat –n command.

b. What type of information does the netstat –n command return? established

c. Where does the IP address found in Step 1 appear? Is there a port number associated with it? Why or why not?

Pada step 1 tidak ditemukan alamat IP.

Step 4: Display active network connections

a. Ping and record the address.

request time out

b. Open a web browser and enter in the address bar.

c. Go back to the Command Prompt window. Type the netstat –n command again, and then type the command without the –n option. The output looks similar to the following figure, depending on what other network applications and connections are open when you issued the command.

d. What is the difference in the output between the netstat and netstat –n commands?

pada perintah netstat menampilkan Local Address berupa alamat PC, sedangkan perintah netstat -n menampilkan Local Address berupa alamat IP.

e. Write down the connection entries for the client IP address and the IP address of the web server.
Local client IP address and port number:
Foreign IP Address and port number:

f. Are there more netstat entries the second time? established

Step 5: Determine translated addresses

Use the information recorded in steps 2 and 4 and the topology diagram shown at the beginning of the lab to fill in the Address:Port columns.

Step 6: Reflection

a. Port address translation (PAT) is also called NAT with overload. What does the term “overload” refer to?

b. The NAT terminology used in the lab includes four types of addresses: inside-local, inside-global, outside-local, and outside-global. In many connections that pass through NAT routers, two of these addresses are often the same. Which two of these four addresses normally remain unchanged, and why do you think that is the case?


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