CompTIA Network+ exam Chapter 8

What is the subnet for host ID 172.16.3.65/23?

A /23 is 255.255.254.0. The third octet is a block size of 2 (256-254=2). 0, 2, 4. The host is in the subnet 172.16.2.0 Valid hosts are 172.16.2.1 up to 3.254 Broadcast is 172.16.3.255 Next valid subnet 172.16.4.0

192.168.100.37/28

192.168.100.37/28. A /28 is 255.255.255.240. The fourth octet is a block size of 16 (256-240=16). Just count by 16s until you pass 37 (0, 16, 32, 48) The valid subnet is 192.168.100.32 Valid hosts are 192.168.100.33 up to 46 Broadcast is 192.168.100.47 Next valid subnet is 192.168.100.48

You have an interface on a router with the IP address of 192.168.192.10/29. What is the broadcast address the hosts will use on this LAN?

192.168.192.15 A /29 (255.255.255.248) has a block size of 8 in the fourth octet. This means the subnets are 0, 8, 16, 24, and so on. 10 is in the 8 subnet. The next subnet is 16, so 15 is the broadcast address.

The network address of 172.16.0.0/19 provides how many subnets and hosts?

8 subnets, 8,190 hosts each A CIDR address of /19 is 255.255.224.0. This is a Class B address, so that is only 3 subnet bits, but it provides 13 host bits, or 8 subnets, each with 8,190 hosts.

Default subnet masks

Class Format Default subnet mask A network.host.host.host 255.0.0.0 B network.network.host.host 255.255.0.0 C network.network.network.host 255.255.255.0

You have been hired by a company named Secure World Inc. You are designing a TCP/IP-based network. The company has purchased a C-class IP address. You are required to segment the network. What will you do to accomplish the task?

Configure subnetting on the network.

When configuring the IP settings on a computer on one subnet to ensure that it can communicate with a computer on another subnet, which of the following is desirable?

Configure the computer with a default gateway that matches the IP address of the interface of the router that is attached to the same subnet as the computer. A computer should be configured with an IP address that is unique throughout the reachable internetwork. It should be configured with a subnet mask that matches those of all other devices on its local subnet, but not necessarily one that matches the mask used on any other subnet. It should also be configured with a default gateway that matches its local router's interface IP address.

What are the advantages of implementing NAT (Network Address Translation) on a device?

Conserves legally registered addresses. Reduces address overlap occurrences. Increases flexibility when connecting to the Internet. Eliminates address renumbering as the network changes.

Click to select the steps for calculating subnets, and then drag them in the correct order.

Determine the interesting octet by determining the last octet in the subnet mask to contain a 1. Determine the block size by subtracting the decimal value in the subnet's interesting octet from 256. Determine the first subnet by setting all the borrowed bits (which are bits in the subnet mask beyond the bits in the classful subnet mask) to 0. Determine additional subnets by taking the first subnet and counting by the block size increment in the interesting octet.

You receive a call from a user who is complaining that they cannot get on the Internet. You have them verify their IP address, mask, and default gateway. The IP address is 10.0.37.144, with a subnet mask of 255.255.254.0. The default gateway is 10.0.38.1. What is the problem?

Incorrect gateway IP The host ID Class A of 10.0.37.144 with a 255.255.254.0 mask is in the 10.0.36.0 subnet. The third octet has a block size of 2 (256-254=2), so the next subnet is 10.0.38.0, which makes the broadcast address 10.0.37.255. The default gateway address of 10.0.38.1 is not in the same subnet as the host.

Which of the following are advantages of subnetting a network?

It reduces traffic congestion. It optimizes the IP address space.

Classless Inter-Domain Routing (CIDR)

It's basically the method that Internet service providers (ISPs) use to allocate a number of addresses to a company or a home connection.

NAT Names

Name: Inside local Meaning: Name of the inside source address before translation Name: Outside local Meaning: Name of the destination host before translation Name: Inside global Meaning: Name of the inside host after translation Name: Outside global Meaning: Name of the outside destination host after translation

Which of the following is required to allow sharing of a single public IP address?

PAT

If you want to verify the local IP stack on your computer, what would you do?

ping 127.0.0.1

What is the CIDR (Classless Inter-Domain Routing) value for a Class B default mask?

/16

On a network, which mask should you use on point-to-point WAN links in order to reduce the waste of IP addresses?

/30 A point-to-point link uses only two hosts. A /30, or 255.255.255.252, mask provides two hosts per subnet.

Identify the valid public IP addresses.

11.20.2.1 174.16.0.1

How many hosts per subnet are possible for the subnet mask 255.255.192.0?

16,382

Subnetting a Class B Address: The Fast Way! Example 1

172.16.0.0 = Network address 255.255.128.0 = Subnet mask Subnets? 2^1 = 2 (same as Class C). Hosts? 2^15 - 2 = 32,766 (7 bits in the third octet, and 8 in the fourth). Valid subnets? 256 - 128 = 128. 0, 128. Remember that subnetting in Class B starts in the third octet, so the subnet numbers are really 0.0 and 128.0. We use them in the third octet and add a 0 in the fourth octet for the network address. The following table shows the 0.0, and 128.0 subnets, the valid host ranges of each, and the broadcast address of each subnet: Network 172.16.0.0 First Usable IP 172.16.0.1 Last Usable IP 172.16.127.254 Broadcast 172.16.127.255 Network 172.16.128.0 First Usable IP 172.16.128.1 Last Usable IP 172.16.255.254 Broadcast 172.16.255.255

Subnetting a Class B Address: The Fast Way! Example 2

172.16.0.0 = Network address 255.255.192.0 = Subnet mask Subnets? 2^2 = 4. Hosts? 2^14 - 2 = 16,382 (6 bits in the third octet, and 8 in the fourth). Valid subnets? 256 - 192 = 64. 0, 64, 128, 192. Remember that we're in the third octet, so the subnet numbers are really 0.0, 64.0, 128.0, and 192.0 The following table shows the 0.0, 64.0, 128.0, and 192.0 subnets, the valid host ranges of each, and the broadcast address of each subnet: Network 172.16.0.0 First Usable IP 172.16.0.1 Last Usable IP 172.16.63.254 Broadcast 172.16.63.255 Network 172.16.64.0 First Usable IP 172.16.64.1 Last Usable IP 172.16.127.254 Broadcast 172.16.127.255 Network 172.16.128.0 First Usable IP 172.16.128.1 Last Usable IP 172.16.191.254 Broadcast 172.16.191.255 Network 172.16.192.0 First Usable IP 172.16.192.1 Last Usable IP 172.16.255.254 Broadcast 172.16.255.255

What is the highest usable address on the 172.16.1.0/24 network?

172.16.1.254 A 24-bit mask, or prefix length, indicates that the entire fourth octet is used for host identification. In a special case, such as this, it is simpler to visualize the all-zeros value (172.16.1.0) and the all-ones value (172.16.1.255). The highest usable address, the last one before the all-ones value, is 172.16.1.254.

If an Ethernet port on a router was assigned an IP address of 172.16.112.1/25, what would be the subnet address of this host?

172.16.112.0 A /25 mask is 255.255.255.128. Used with a Class B network, the third and fourth octets are used for subnetting with a total of 9 subnet bits: 8 bits in the third octet and 1 bit in the fourth octet. Because there is only 1 bit in the fourth octet, the bit is either off or on "which is a value of 0 or 128. The host in the question is in the 0 subnet, which has a broadcast address of 127 because 128 is the next subnet.

You have a network with a subnet of 172.16.17.0/22. Which of the following is a valid host address?

172.16.18.255 255.255.252.0 A Class B network ID with a /22 mask is 255.255.252.0, with a block size of 4 in the third octet. The network address in the question is in subnet 172.16.16.0 with a broadcast address of 172.16.19.255. Only option E has the correct subnet mask listed, and 172.16.18.255 is a valid host.

Your router has the following IP address on Ethernet0: 172.16.2.1/23. Which of the following can be valid host IDs on the LAN interface attached to the router? (Choose two.)

172.16.2.255 172.16.3.0 The router's IP address on the E0 interface is 172.16.2.1/23, which is a 255.255.254.0. This makes the third octet a block size of 2. The router's interface is in the 2.0 subnet, and the broadcast address is 3.255 because the next subnet is 4.0. The valid host range is 2.1 through 3.254. The router is using the first valid host address in the range.

192.168.100.99/25

192.168.100.99/25. A /25 is 255.255.255.128. The fourth octet is a block size of 128. 0, 128. The host is in the 0 subnet, broadcast of 127. Valid hosts are 1-126.

192.168.100.99/26

192.168.100.99/26. A /26 is 255.255.255.192. The fourth octet has a block size of 64. 0, 64, 128. The host is in the 64 subnet, broadcast of 127. Valid hosts are 65-126.

What is the subnetwork address for a host with the IP address 200.10.5.168/28?

200.10.5.160 A /28 is 255.255.255.240, which means that our block size is 16 (256-240=16) in the fourth octet. 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, and so on. The host is in the 160 subnet.

What is the subnetwork address for a host with the IP address 200.10.5.68/28?

200.10.5.64 This is a pretty simple question. A /28 is 255.255.255.240, which means that our block size is 16 (256-240=16) in the fourth octet (0, 16, 32, 48, 64, 80, and so on). The host is in the 64 subnet.

Select the default subnet masks for the given IP format from the lists given in the figure.

Class: A Format: network.host.host.host Default subnet mask: 255.0.0.0 Class: B Format: network.network.host.host Default subnet mask: 255.255.0.0 Class: C Format: network.network.network.host Default subnet mask: 255.255.255.0

A network administrator is connecting two hosts directly through their Ethernet interfaces, as shown in the illustration. Ping attempts between the hosts are unsuccessful. What can be done to provide connectivity between the hosts? (Choose two.)

A crossover cable should be used in place of the straight-through cable. The subnet masks should be set to 255.255.255.0. First, if you have two hosts directly connected, as shown in the graphic, then you need a crossover cable. A straight-through cable won't work. Second, the hosts have different masks, which puts them in different subnets. The easy solution is just to set both masks to (/24).

You have a Class B network and need 29 subnets. What is your mask?

A default Class B is 255.255.0.0 A Class B 255.255.255.0 mask is 256 subnets (2^8=256), each with 254 hosts (2^8-2=254). We need fewer subnets. If we use 255.255.240.0, this provides 16 subnets (2^4=16). Let's add one more subnet bit. 255.255.248.0. This is 5 bits of subnetting, which provides 32 subnets (2^5=32). This is our best answer, a /21.

Subnet Masks

A subnet mask is a 32-bit value that allows the recipient of IP packets to distinguish the network ID portion of the IP address from the host ID portion of the IP address.

Advantages and Disadvantages of NAT

Advantages Conserves legally registered addresses. Reduces address overlap occurrences. Increases flexibility when connecting to the Internet. Eliminates address renumbering as the network changes. Disadvantages Translation introduces switching path delays. Loss of end-to-end IP traceability. Certain applications will not function with NAT enabled.

Private addresses

Class A 10.0.0.0-10.255.255.255 Class B 172.16.0.0-172.31.255.255 Class C 192.168.0.0-192.168.255.255

If a host on a network has the address 172.16.45.14/30, what is the subnetwork this host belongs to?

172.16.45.12 A /30, regardless of the class of address, has a 252 in the fourth octet. This means we have a block size of 4 and our subnets are 0, 4, 8, 12, 16, and so on. Address 14 is obviously in the 12 subnet.

Subnetting a Class C Address: The Fast Way! Example 1

192.168.10.0 = Network address 255.255.255.128 = Subnet mask How many subnets? Because 128 is 1 bit on (10000000), the answer is 2^1 = 2. How many hosts per subnet? We have 7 host bits off (10000000), so the equation is 2^7 - 2 = 126 hosts. What are the valid subnets? 256 - 128 = 128. Remember, we'll start at zero and count in our block size, so our subnets are 0, 128. What's the broadcast address for each subnet? The number right before the value of the next subnet is all host bits turned on and equals the broadcast address. For the 0 subnet, the next subnet is 128, so the broadcast of the 0 subnet is 127. What are the valid hosts? These are the numbers between the subnet and broadcast address. The easiest way to find the hosts is to write out the subnet address and the broadcast address. This way, the valid hosts are obvious. The following table shows the 0 and 128 subnets, the valid host ranges of each, and the broadcast address of both subnets: 192.168.10.0 Last host 192.168.10.126 Broadcast 192.168.10.127 192.168.10.128 Last Host 192.168.10.254 Broadcast 192.168.10.255

Subnetting a Class C Address: The Fast Way! Example 2

192.168.10.0 = Network address 255.255.255.192 = Subnet mask How many subnets? Because 192 is 2 bits on (11000000), the answer is 2^2 = 4 subnets. How many hosts per subnet? We have 6 host bits off (11000000), so the equation is 2^6 - 2 = 62 hosts. What are the valid subnets? 256 - 192 = 64. Remember, we start at zero and count in our block size, so our subnets are 0, 64, 128, and 192. What's the broadcast address for each subnet? The number right before the value of the next subnet is all host bits turned on and equals the broadcast address. For the 0 subnet, the next subnet is 64, so the broadcast address for the 0 subnet is 63. What are the valid hosts? These are the numbers between the subnet and broadcast address. The easiest way to find the hosts is to write out the subnet address and the broadcast address. This way, the valid hosts are obvious. The following table shows the 0, 64, 128, and 192 subnets, the valid host ranges of each, and the broadcast address of each subnet: Network 192.168.10.0 First Usable IP 192.168.10.1 Last Usable IP 192.168.10.62 Broadcast 192.168.10.63 Network 192.168.10.64 First Usable IP 192.168.10.65 Last Usable IP 192.168.10.126 Broadcast 192.168.10.127 Network 192.168.10.128 First Usable IP 192.168.10.129 Last Usable IP 192.168.10.190 Broadcast 192.168.10.191 Network 192.168.10.192 First Usable IP 192.168.10.193 Last Usable IP 192.168.10.254 Broadcast 192.168.10.255

Using the following illustration, what would be the IP address of E0 if you were using the eighth subnet? The network ID is 192.168.10.0/28, and you need to use the last available IP address in the range. The 0 subnet should not be considered valid for this question. Router ==> Switch ==> 2 host terminals

192.168.10.142 A /28 is a 255.255.255.240 mask. Let's count to the ninth subnet (we need to find the broadcast address of the eighth subnet, so we need to count to the ninth subnet). We start at 16 (remember, the question stated that we will not use subnet 0, so we start at 16, not 0): 16, 32, 48, 64, 80, 96, 112, 128, 144. The eighth subnet is 128, and the next subnet is 144, so our broadcast address of the 128 subnet is 143. This makes the host range 129-142. 142 is the last valid host.

Using the following illustration, what would be the IP address of E0 if you were using the first subnet? The network ID is 192.168.10.0/28, and you need to use the last available IP address in the range. Again, the zero subnet should not be considered valid for this question. Router ==> Switch ==> 2 host terminals

192.168.10.30 A /28 is a 255.255.255.240 mask. The first subnet is 16 (remember that the question stated not to use subnet 0), and the next subnet is 32, so our broadcast address is 31. This makes our host range 17-30. 30 is the last valid host.

192.168.100.17/29

192.168.100.17/29. A /29 is 255.255.255.248. The fourth octet is a block size of 8. 0, 8, 16, 24. The host is in the 16 subnet, broadcast of 23. Valid hosts are 17-22.

192.168.100.25/30

192.168.100.25/30. A /30 is 255.255.255.252. The fourth octect is a block size of 4 (256-252=4) The valid subnet is 192.168.100.24 Valid hosts are 192.168.100.25 and 26 Broadcast is 192.168.100.27 Next valid subnet is 192.168.100.28

192.168.100.66/27

192.168.100.66/27. A /27 is 255.255.255.224. The fourth octet is a block size of 32 (256-240=32). Count by 32s until you pass the host address of 66 (0, 32, 64, 96) The valid subnet is 192.168.100.64 Valid hosts are 192.168.100.65 up to 94 Broadcast is 192.168.100.95 Next valid subnet is 192.168.100.96

Rick works as a network administrator for NetTech Inc. The company has a Windows 2008 domain-based network. The network comprises 14 Windows 2008 member servers and 175 Windows 7 Ultimate client computers. All computers on the network are using the 10.0.0.0/8 addressing scheme. Rick decides to place all member servers into a separate subnet that uses the 192.168.1.0 addressing scheme. Rick also plans to add 20 more member servers in this subnet. Therefore, he will now require 34 servers. For this purpose, Rick wants to configure a new subnet mask. The subnet mask must be capable of providing IP addresses to 34 member servers. Which of the following subnet masks will Rick use to accomplish this?

255.255.255.192 provides 62 hosts 255.255.255.224 provides 30 hosts 255.255.255.240 provides 14 hosts 255.255.255.248 provides 6 hosts

What is the maximum number of IP addresses that can be assigned to hosts on a local subnet that uses the 255.255.255.224 subnet mask?

30 A /27 (255.255.255.224) is 3 bits ON and 5 bits OFF. This provides 8 subnets, each with 30 hosts. Does it matter if this mask is used with a Class A, B, or C network address? Not at all. The number of host bits would never change.

You have an interface on a router with the IP address of 192.168.192.10/29. Including the router interface, how many hosts can have IP addresses on the LAN attached to the router interface?

6 A /29 (255.255.255.248), regardless of the class of address, has only 3 host bits. Six hosts is the maximum number of hosts on this LAN, including the router interface.

How many hosts are available with a Class C /29 mask?

A /29 is 255.255.255.248, which is 5 subnet bits and 3 host bits. This is only 6 hosts per subnet.

What is the broadcast address of 192.168.192.10/29?

A /29 is 255.255.255.248. This is a block size of 8 in the fourth octet. 0, 8, 16. The host is in the 8 subnet, and broadcast is 15.

You have one IP address provided from your ISP with a /30 mask. However, you have 300 users that need to access the Internet. What technology will you use to implement a solution?

PAT Network Address Translation can allow up to 65,000 hosts to get onto the Internet with one IP address by using Port Address Translation (PAT).

Which technology is used to allow a pool of users to share one global IP address for Internet access?

Port address translation

Advantages from subnetting

Reduced Network Traffic Optimized Network Performance Simplified Management Facilitated Spanning of Large Geographical Distances

On which of the following devices are you most likely to be able to implement NAT?

Router Devices with Layer 3 awareness, such as routers and firewalls, are the only ones that can manipulate the IP header in support of NAT.

You have a Class A host of 10.0.0.110/25. It needs to communicate to a host with an IP address of 10.0.0.210/25. Which of the following devices do you need to use in order for these hosts to communicate?

Router Don't freak because this is a Class A. What is your subnet mask? 255.255.255.128. Regardless of the class of address, this is a block size of 128 (256-128=128) in the fourth octet. The subnets are 0 and 128. First host is in subnet 10.0.0.0 Host range is 10.0.0.1-126 Broadcast 10.0.0.127 Second host is in subnet 10.0.0.128 Host range is 10.0.0.129-254 Broadcast 10.0.0.255. You need a router for these two hosts to communicate because they are in different subnets.

Which of the following address translation types is described in the statement below? "It performs a manual translation of one IP address to a different one. It is typically used to translate destination IP address in packets that reaches to the translation device (like router) for the LAN. In this type of address translation, a manual translation is performed between two addresses, and possibly port numbers."

Static NAT

Drag the types of network address translation from the bottom onto their matching descriptions on the top.

Static NAT (SNAT): It's designed to allow one-to-one mapping between local and global addresses. Dynamic NAT (DNAT): It gives you the ability to map an unregistered IP address to a registered IP address from a pool of registered IP addresses. Overloading: It maps multiple unregistered IP addresses to a single registered IP address (many-to-one) by using different ports.

Types of Network Address Translation (NAT)

Static NAT (SNAT): This type of NAT is designed to allow one-to-one mapping between local and global addresses. Keep in mind that the static version requires you to have one real Internet IP address for every host on your network. Dynamic NAT (DNAT): This version gives you the ability to map an unregistered IP address to a registered IP address from a pool of registered IP addresses. You don't have to statically configure your router to map an inside-to-an-outside-address as you would using static NAT, but you do have to have enough real, bona-fide IP addresses for everyone who's going to be sending packets to and receiving them from the Internet. Overloading: This is the most popular type of NAT configuration. Understand that overloading really is a form of dynamic NAT that maps multiple unregistered IP addresses to a single registered IP address—many-to-one—by using different ports. Now, why is this so special? Well, because it's also known as Port Address Translation (PAT). And by using PAT (NAT Overload), you get to have thousands of users connect to the Internet using only one real global IP address—pretty slick, yeah? Seriously, NAT Overload is the real reason we haven't run out of valid IP address on the Internet. Really—I'm not joking.

Subnet mask and its equivalent CIDR slash notation

Subnet Mask CIDR Value 255.0.0.0 /8 255.128.0.0 /9 255.192.0.0 /10 255.224.0.0 /11 255.240.0.0 /12 255.248.0.0 /13 255.252.0.0 /14 255.254.0.0 /15 255.255.0.0 /16 255.255.128.0 /17 255.255.192.0 /18 255.255.224.0 /19 255.255.240.0 /20 255.255.248.0 /21 255.255.252.0 /22 255.255.254.0 /23 255.255.255.0 /24 255.255.255.128 /25 255.255.255.192 /26 255.255.255.224 /27 255.255.255.240 /28 255.255.255.248 /29 255.255.255.252 /30 We can't use a /31 or /32 because, remember, we have to leave at least 2 host bits for assigning IP addresses to hosts.

Drag the subnet masks to match them with their CIDR values.

Subnet Mask CIDR Value 255.255.192.0 /18 255.255.255.128 /25 255.255.255.248 /29 255.224.0.0 /11 255.255.255.252 /30

Drag the subnet masks from the bottom onto their matching hosts per subnet values on the top.

Subnet Mask Hosts per Subnet 255.255.255.128 126 255.255.255.192 62 255.255.255.224 30 255.255.255.240 14 255.255.255.248 6

Rick, an administrator of a TCP/IP network, wants to achieve the following goals: Reduce congestion of network traffic. Optimize the utilization of the IP address space. Which of the following technologies may help him accomplish the task?

Subnetting

Which of the following terms best describes the process through which a TCP/IP network is subdivided by using parts of the node address as network IDs?

Subnetting

If you are forced to replace a router that has failed to the point that you are unable to access its current configuration to aid in setting up interface addresses on the new router, which of the following can you reference for assistance?

The default-gateway settings on computers from each subnet that the old router interconnected. The best method here is to check the configuration of devices that were using the old router as a gateway to the rest of the internetwork. Routers do not periodically cache their configurations to servers of any sort. You might have copied the old router's configuration to a TFTP server or the like, but failing that, you will have to rebuild the configuration from scratch, which might well be much more than interface addresses. Therefore, keeping a copy of the router's current configuration somewhere other than on the router is a wise choice. Routers don't auto-configure themselves; we wouldn't want them to.

What are the disadvantages of implementing NAT (Network Address Translation) on a device?

Translation introduces switching path delays. Loss of end-to-end IP traceability. Certain applications will not function with NAT enabled.

What it means 192.168.10.32/28?

When you receive a block of addresses from an ISP, what you get will look something like this: 192.168.10.32/28. This is telling you what your subnet mask is. The slash notation (/) means how many bits are turned on (1s). Obviously, the maximum could only be /32 because a byte is 8 bits and there are 4 bytes in an IP address: 4 × 8 = 32. But keep in mind that the largest subnet mask available (regardless of the class of address) can only be a /30 because you have to keep at least 2 bits for host bits.