Computer Networks Numerical Mcq Set 2

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1.  How long is an IPv6 address?
A. 32 bits
B. 128 bytes
C. 64 bits
D. 128 bits

Answer: Option D

Explanation:

An IPv6 address is 128 bits long.
2.  You have 10 users plugged into a hub running 10Mbps half-duplex. There is a server connected to the switch running 10Mbps half-duplex as well. How much bandwidth does each host have to the server?
A. 100 kbps
B. 1 Mbps
C. 2 Mbps
D. 10 Mbps

Answer: Option D

Explanation:

Each device has 10 Mbps to the server.
 3. Which of the following is the valid host range for the subnet on which the IP address 192.168.168.188 255.255.255.192 resides?
A. 192.168.168.129-190
B. 192.168.168.129-191
C. 192.168.168.128-190
D. 192.168.168.128-192

Answer: Option A

Explanation:

256 – 192 = 64. 64 + 64 = 128. 128 + 64 = 192. The subnet is 128, the broadcast address is 191, and the valid host range is the numbers in between, or 129-190.
4.  How often are BPDUs sent from a layer 2 device?
A. Never
B. Every 2 seconds
C. Every 10 minutes
D. Every 30 seconds

Answer: Option B

Explanation:

Every 2 seconds, BPDUs are sent out from all active bridge ports by default.

5. Which of the following is private IP address?
A. 12.0.0.1
B. 168.172.19.39
C. 172.15.14.36
D. 192.168.24.43

Answer: Option D

Explanation:

Class A private address range is 10.0.0.0 through 10.255.255.255. Class B private address range is 172.16.0.0 through 172.31.255.255, and Class C private address range is 192.168.0.0 through 192.168.255.255.
6. 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?

  1. 172.16.1.100
  2. 172.16.1.198
  3. 172.16.2.255
  4. 172.16.3.0
A. 1 only
B. 2 and 3 only
C. 3 and 4 only
D. None of the above

Answer: Option C

Explanation:

The router’s IP address on the E0 interface is 172.16.2.1/23, which is 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.

7. Which two statements describe the IP address 10.16.3.65/23?

  1. The subnet address is 10.16.3.0 255.255.254.0.
  2. The lowest host address in the subnet is 10.16.2.1 255.255.254.0.
  3. The last valid host address in the subnet is 10.16.2.254 255.255.254.0.
  4. The broadcast address of the subnet is 10.16.3.255 255.255.254.0.
A. 1 and 3
B. 2 and 4
C. 1, 2 and 4
D. 2, 3 and 4

Answer: Option B

Explanation:

The mask 255.255.254.0 (/23) used with a Class A address means that there are 15 subnet bits and 9 host bits. The block size in the third octet is 2 (256 – 254). So this makes the subnets in the interesting octet 0, 2, 4, 6, etc., all the way to 254. The host 10.16.3.65 is in the 2.0 subnet. The next subnet is 4.0, so the broadcast address for the 2.0 subnet is 3.255. The valid host addresses are 2.1 through 3.254.
8. 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?
A. 14
B. 15
C. 16
D. 30

Answer: Option D

Explanation:

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.

9. You need to subnet a network that has 5 subnets, each with at least 16 hosts. Which classful subnet mask would you use?
A. 255.255.255.192
B. 255.255.255.224
C. 255.255.255.240
D. 255.255.255.248

Answer: Option B

Explanation:

You need 5 subnets, each with at least 16 hosts. The mask 255.255.255.240 provides 16 subnets with 14 hosts-this will not work. The mask 255.255.255.224 provides 8 subnets, each with 30 hosts. This is the best answer.

 

10. You have a network that needs 29 subnets while maximizing the number of host addresses available on each subnet. How many bits must you borrow from the host field to provide the correct subnet mask?
A. 2
B. 3
C. 4
D. 5

Answer: Option D

Explanation:

A 240 mask is 4 subnet bits and provides 16 subnets, each with 14 hosts. We need more subnets, so let’s add subnet bits. One more subnet bit would be a 248 mask. This provides 5 subnet bits (32 subnets) with 3 host bits (6 hosts per subnet). This is the best answer.

11. If an Ethernet port on a router were assigned an IP address of 172.16.112.1/25, what would be the valid subnet address of this host?
A. 172.16.112.0
B. 172.16.0.0
C. 172.16.96.0
D. 172.16.255.0

Answer: Option A

Explanation:

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. Since 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 since 128 is the next subnet.

12. 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?
A. 6
B. 8
C. 30
D. 32

Answer: Option A

Explanation:

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.

13. What is the subnetwork number of a host with an IP address of 172.16.66.0/21?
A. 172.16.36.0
B. 172.16.48.0
C. 172.16.64.0
D. 172.16.0.0

Answer: Option C

Explanation:

A /21 is 255.255.248.0, which means we have a block size of 8 in the third octet, so we just count by 8 until we reach 66. The subnet in this question is 64.0. The next subnet is 72.0, so the broadcast address of the 64 subnet is 71.255.

14. The network address of 172.16.0.0/19 provides how many subnets and hosts?
A. 7 subnets, 30 hosts each
B. 8 subnets, 8,190 hosts each
C. 8 subnets, 2,046 hosts each
D. 7 subnets, 2,046 hosts each

Answer: Option B

Explanation:

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.

15. You need to configure a server that is on the subnet 192.168.19.24/29. The router has the first available host address. Which of the following should you assign to the server?
A. 192.168.19.0 255.255.255.0
B. 192.168.19.33 255.255.255.240
C. 192.168.19.26 255.255.255.248
D. 192.168.19.31 255.255.255.248

Answer: Option C

Explanation:

A /29 is 255.255.255.248, which is a block size of 8 in the fourth octet. The subnets are 0, 8, 16, 24, 32, 40, etc. 192.168.19.24 is the 24 subnet, and since 32 is the next subnet, the broadcast address for the 24 subnet is 31. 192.168.19.26 is the only correct answer.

16. 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?
A. 192.168.192.15
B. 192.168.192.31
C. 192.168.192.63
D. 192.168.192.127

Answer: Option A

Explanation:

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, etc. 10 is in the 8 subnet. The next subnet is 16, so 15 is the broadcast address.
17. Which statement(s) about IPv6 addresses are true?

  1. Leading zeros are required.
  2. Two colons (::) are used to represent successive hexadecimal fields of zeros.
  3. Two colons (::) are used to separate fields.
  4. A single interface will have multiple IPv6 addresses of different types.
A. 1 and 3
B. 2 and 4
C. 1, 3 and 4
D. All of the above

Answer: Option B

Explanation:

In order to shorten the written length of an IPv6 address, successive fields of zeros may be replaced by double colons. In trying to shorten the address further, leading zeros may also be removed. Just as with IPv4, a single device’s interface can have more than one address; with IPv6 there are more types of addresses and the same rule applies. There can be link-local, global unicast, and multicast addresses all assigned to the same interface.

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