QUESTION 51:
You have a class B network with a 255.255.255.0 mask. Which of the statements below are true of this network? (Select all valid answers)
A. There are 254 usable subnets.
B. There are 256 usable hosts per subnet.
C. There are 50 usable subnets.
D. There are 254 usable hosts per subnet.
E. There are 24 usable hosts per subnet.
F. There is one usable network.
Explanation:
The default subnet mask for Class B is 255.255.0.0. Thus an extra 8 bits have been used for the network portion, leaving 8 for hosts. The 2n - 2 formula (28 - 2 in this case for both the network and IP hosts) gives us 254 networks and 254 hosts per network.
Incorrect Answers:
B. We must remember to always subtract 2 (one for the network, and one for the broadcast) so the result is 254, not 256.
C, E: No possible network mask would give us this exact number of subnets or hosts.
F. This would be true if this were a class C network, not a class B.
QUESTION 52:
How many usable IP addresses can you get from a conventional Class C address?
A. 128
B. 192
C. 254
D. 256
E. 510
Explanation:
Class Caddresses range from 192.0.0.0 through 223.225.225.225 and default subnet maskof 255.255.255.0. In Class C addresses, the first 24 bits are used as for the network IDwhile only the last 8 bits is used for the host ID. Using the 2n-2 formula, we can calculate that Class C addresses can support a maximum of 254 (28-2) hosts.
Incorrect Answers:
D. Note that the question asked for the number of usable addresses, and not the total number of all addresses. We must subtract 2 for the network and broadcast addresses to calculate the number of usable addresses in any subnet.
QUESTION 53:
Your ISP assigned you a full class B address space. From this, you need at least 300 sub-networks that can support at least 50 hosts each. Which of the subnet masks below are capable of satisfying your needs? (Select two).
A. 255.255.255.0
B. 255.255.255.128
C. 255.255.252.0
D. 255.255.255.224
E. 255.255.255.192
F. 255.255.248.0
Explanation:
Requirement in the question is that the company needs 300 subnets and 50 hosts per subnet.
With 9 bits used for the subnet portion, we get 510 subnets and using the remaining 7 bits for the hosts gives us 126 hosts per subnet. The subnet mask will be 255.255.255.128
With 10 bits used for the subnet portion, we get 1022 subnets and then using the remaining 6 bits for hosts provides 62 hosts per subnet. The subnet mask will be 255.255.255.192 in this case which will also fulfill the requirement.
QUESTION 54:
A Certkiller PC has the IP address 172.16.209.10 /22. What is the subnet of this address?
A. 172.16.42.0
B. 172.16.107.0
C. 172.16.208.0
D. 172.16.252.0
E. 172.16.254.0
Explanation:
172.16.209.10/22 translates to 10101100.00010000.11010001.00001010 in binary form. The network portion is 22 bits, so after the logical AND comparison the network address translates to10101100.00010000.110100001.00001010. Converting the network portion to decimal results in the address 172.16.208.0/22
QUESTION 55:
You've been assigned the CIDR (classless inter domain routing) block of 115.64.4.0/22 from your ISP. Which of the IP addresses below can you use for a host? (Select all valid answers)
A. 115.64.8.32
B. 115.64.7.64
C. 115.64.6.255
D. 115.64.3.255
E. 115.64.5.128
F. 115.64.12.128
Explanation:
115.64.4.0 = 01110011.01000000.00000100.00000000
Subnet mask = 11111111.11111111.11111100.00000000= 255.255.252.0
Subnet number = 01110011.01000000.00000100.00000000= 115.64.4.0
Broadcast = 01110011.01000000.00000111.11111111= 115.64.7.255
Valid address range = 115.64.4.1 - 115.64.7.254
QUESTION 56:
A Certkiller remote office branch is set up as shown in the diagram below:
All of the hosts in the above exhibit are connected with each other via the single Catalyst switch. Which of the following statements correctly describe the addressing scheme of this network? (Select three)
A. The subnet mask in use is 255.255.255.192.
B. The subnet mask in use is 255.255.255.128.
C. The IP address 172.16.1.25 can be assigned to hosts in VLAN1.
D. The IP address 172.16.1.205 can be assigned to hosts in VLAN1
E. The LAN interface of the router is configured with one IP address.
F. The LAN interface of the router is configured with multiple IP addresses.
Explanation:
Based on the diagram above, the subnet mask used for each VLAN is 255.255.255.128.
This means that hosts in VLAN 1 will be addressed 172.16.1.1-172.16.1.126, with
172.16.1.127 being used as the broadcast address. Hosts in VLAN 2 will be addressed
172.16.1.129-172.16.1.254. Because there is only one LAN interface on the router, sub interfaces will be used, so the router's LAN interface will be configured with 2 IP addresses, one for VLAN 1 and 1 for VLAN 2.
Incorrect Answers:
A. This subnet mask will only provide 62 host IP addresses, and the diagram shows that as many as 114 host IP addresses are needed.
D. This IP address can be used in VLAN 2, not VLAN 1.
E. Since there are 2 subnets in this network, each separate network will require a distinct default gateway IP address, so 2 IP addresses will be required on the LAN interface of the router.
QUESTION 57:
(Select three)
A. 172.16.82.255
B. 172.16.95.255
C. 172.16.64.255
D. 172.16.32.255
E. 172.16.47.255
F. 172.16.79.255
Explanation:
The subnets in the network are subnetted Class B addresses. A /20 subnet mask means that the subnet addresses increment by a factor of 16. For example: 172.16.16.0, 172.16.32.0, 172.16.48.0, 172.16.64.0 etc. The broadcast address is the last IP address before the next subnet address.
B. The switch IP address (172.16.82.90) is in the 172.16.80.0 subnet. 172.16.95.255 is the broadcast address for the 172.16.80.0 subnet.
E. This is the broadcast address for the 172.16.32.0 subnet.
F. This is the broadcast address for the 172.16.64.0 subnet.
QUESTION 58:
Which one of the following varieties of NAT utilizes different ports to map multiple IP addresses to a single globally registered IP address?
A. Static NAT
B. Port loading
C. NAT Overloading
D. Dynamic NAT
E. None of the above
Explanation:
Port address translation, or NAT overloading, uses transport layer port information to dynamically create NAT entries. This is also known as one to many network address translation.
Incorrect Answers:
A. Static NAT is known as one to one NAT, and is used to map a single IP address to a single registered IP address. It is often used for servers that need to be accessed via the Internet.
B, D: This is the incorrect term, and is not used.
QUESTION 59:
On the topic of VLSM, which one of the following statements best describes the concept of the route aggregation?
A. Deleting unusable addresses through the creation of many subnets.
B. Combining routes to multiple networks into one supernet.
C. Reclaiming unused space by means of changing the subnet size.
D. Calculating the available host addresses in the AS.
Explanation:
In the networking world route aggregate means combining routes to multiple networks into one. This is also known as route summarization or supernetting. It is normally used to reduce the number of route entries in the routing table by advertising numerous routes into one larger route.
Reference: CCNA Self-Study CCNA ICND exam certification Guide (Cisco Press,
ISBN 1-58720-083-X) Page 236.
QUESTION 60:
You have a single Class C IP address and a point-to-point serial link that you want to implement VLSM on. Which subnet mask is the most efficient?
A. 255.255.255.0
B. 255.255.255.240
C. 255.255.255.248
D. 255.255.255.252
E. 255.255.255.254
Explanation:
For a single point to point link, only 2 IP addresses are required, one for the serial interface of the router at each end. Therefore, the 255.255.255.252 subnet mask is often used for these types of links, as no IP addresses are wasted.
You have a class B network with a 255.255.255.0 mask. Which of the statements below are true of this network? (Select all valid answers)
A. There are 254 usable subnets.
B. There are 256 usable hosts per subnet.
C. There are 50 usable subnets.
D. There are 254 usable hosts per subnet.
E. There are 24 usable hosts per subnet.
F. There is one usable network.
Explanation:
The default subnet mask for Class B is 255.255.0.0. Thus an extra 8 bits have been used for the network portion, leaving 8 for hosts. The 2n - 2 formula (28 - 2 in this case for both the network and IP hosts) gives us 254 networks and 254 hosts per network.
Incorrect Answers:
B. We must remember to always subtract 2 (one for the network, and one for the broadcast) so the result is 254, not 256.
C, E: No possible network mask would give us this exact number of subnets or hosts.
F. This would be true if this were a class C network, not a class B.
QUESTION 52:
How many usable IP addresses can you get from a conventional Class C address?
A. 128
B. 192
C. 254
D. 256
E. 510
Explanation:
Class Caddresses range from 192.0.0.0 through 223.225.225.225 and default subnet maskof 255.255.255.0. In Class C addresses, the first 24 bits are used as for the network IDwhile only the last 8 bits is used for the host ID. Using the 2n-2 formula, we can calculate that Class C addresses can support a maximum of 254 (28-2) hosts.
Incorrect Answers:
D. Note that the question asked for the number of usable addresses, and not the total number of all addresses. We must subtract 2 for the network and broadcast addresses to calculate the number of usable addresses in any subnet.
QUESTION 53:
Your ISP assigned you a full class B address space. From this, you need at least 300 sub-networks that can support at least 50 hosts each. Which of the subnet masks below are capable of satisfying your needs? (Select two).
A. 255.255.255.0
B. 255.255.255.128
C. 255.255.252.0
D. 255.255.255.224
E. 255.255.255.192
F. 255.255.248.0
Explanation:
Requirement in the question is that the company needs 300 subnets and 50 hosts per subnet.
With 9 bits used for the subnet portion, we get 510 subnets and using the remaining 7 bits for the hosts gives us 126 hosts per subnet. The subnet mask will be 255.255.255.128
With 10 bits used for the subnet portion, we get 1022 subnets and then using the remaining 6 bits for hosts provides 62 hosts per subnet. The subnet mask will be 255.255.255.192 in this case which will also fulfill the requirement.
QUESTION 54:
A Certkiller PC has the IP address 172.16.209.10 /22. What is the subnet of this address?
A. 172.16.42.0
B. 172.16.107.0
C. 172.16.208.0
D. 172.16.252.0
E. 172.16.254.0
Explanation:
172.16.209.10/22 translates to 10101100.00010000.11010001.00001010 in binary form. The network portion is 22 bits, so after the logical AND comparison the network address translates to10101100.00010000.110100001.00001010. Converting the network portion to decimal results in the address 172.16.208.0/22
QUESTION 55:
You've been assigned the CIDR (classless inter domain routing) block of 115.64.4.0/22 from your ISP. Which of the IP addresses below can you use for a host? (Select all valid answers)
A. 115.64.8.32
B. 115.64.7.64
C. 115.64.6.255
D. 115.64.3.255
E. 115.64.5.128
F. 115.64.12.128
Explanation:
115.64.4.0 = 01110011.01000000.00000100.00000000
Subnet mask = 11111111.11111111.11111100.00000000= 255.255.252.0
Subnet number = 01110011.01000000.00000100.00000000= 115.64.4.0
Broadcast = 01110011.01000000.00000111.11111111= 115.64.7.255
Valid address range = 115.64.4.1 - 115.64.7.254
QUESTION 56:
A Certkiller remote office branch is set up as shown in the diagram below:
All of the hosts in the above exhibit are connected with each other via the single Catalyst switch. Which of the following statements correctly describe the addressing scheme of this network? (Select three)
A. The subnet mask in use is 255.255.255.192.
B. The subnet mask in use is 255.255.255.128.
C. The IP address 172.16.1.25 can be assigned to hosts in VLAN1.
D. The IP address 172.16.1.205 can be assigned to hosts in VLAN1
E. The LAN interface of the router is configured with one IP address.
F. The LAN interface of the router is configured with multiple IP addresses.
Explanation:
Based on the diagram above, the subnet mask used for each VLAN is 255.255.255.128.
This means that hosts in VLAN 1 will be addressed 172.16.1.1-172.16.1.126, with
172.16.1.127 being used as the broadcast address. Hosts in VLAN 2 will be addressed
172.16.1.129-172.16.1.254. Because there is only one LAN interface on the router, sub interfaces will be used, so the router's LAN interface will be configured with 2 IP addresses, one for VLAN 1 and 1 for VLAN 2.
Incorrect Answers:
A. This subnet mask will only provide 62 host IP addresses, and the diagram shows that as many as 114 host IP addresses are needed.
D. This IP address can be used in VLAN 2, not VLAN 1.
E. Since there are 2 subnets in this network, each separate network will require a distinct default gateway IP address, so 2 IP addresses will be required on the LAN interface of the router.
QUESTION 57:
(Select three)
A. 172.16.82.255
B. 172.16.95.255
C. 172.16.64.255
D. 172.16.32.255
E. 172.16.47.255
F. 172.16.79.255
Explanation:
The subnets in the network are subnetted Class B addresses. A /20 subnet mask means that the subnet addresses increment by a factor of 16. For example: 172.16.16.0, 172.16.32.0, 172.16.48.0, 172.16.64.0 etc. The broadcast address is the last IP address before the next subnet address.
B. The switch IP address (172.16.82.90) is in the 172.16.80.0 subnet. 172.16.95.255 is the broadcast address for the 172.16.80.0 subnet.
E. This is the broadcast address for the 172.16.32.0 subnet.
F. This is the broadcast address for the 172.16.64.0 subnet.
QUESTION 58:
Which one of the following varieties of NAT utilizes different ports to map multiple IP addresses to a single globally registered IP address?
A. Static NAT
B. Port loading
C. NAT Overloading
D. Dynamic NAT
E. None of the above
Explanation:
Port address translation, or NAT overloading, uses transport layer port information to dynamically create NAT entries. This is also known as one to many network address translation.
Incorrect Answers:
A. Static NAT is known as one to one NAT, and is used to map a single IP address to a single registered IP address. It is often used for servers that need to be accessed via the Internet.
B, D: This is the incorrect term, and is not used.
QUESTION 59:
On the topic of VLSM, which one of the following statements best describes the concept of the route aggregation?
A. Deleting unusable addresses through the creation of many subnets.
B. Combining routes to multiple networks into one supernet.
C. Reclaiming unused space by means of changing the subnet size.
D. Calculating the available host addresses in the AS.
Explanation:
In the networking world route aggregate means combining routes to multiple networks into one. This is also known as route summarization or supernetting. It is normally used to reduce the number of route entries in the routing table by advertising numerous routes into one larger route.
Reference: CCNA Self-Study CCNA ICND exam certification Guide (Cisco Press,
ISBN 1-58720-083-X) Page 236.
QUESTION 60:
You have a single Class C IP address and a point-to-point serial link that you want to implement VLSM on. Which subnet mask is the most efficient?
A. 255.255.255.0
B. 255.255.255.240
C. 255.255.255.248
D. 255.255.255.252
E. 255.255.255.254
Explanation:
For a single point to point link, only 2 IP addresses are required, one for the serial interface of the router at each end. Therefore, the 255.255.255.252 subnet mask is often used for these types of links, as no IP addresses are wasted.
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