Security Questions and Answers updated daily – Networking



10 Security Questions and answers section with explanation for various online exam preparation, various interviews, Networking Security online test. Security Questions with detailed description, explanation will help you to master the topic.

Security Questions

1. You want to create a standard access list that denies the subnet of the following host: 172.16.144.17/21. Which of the following would you start your list with?



SHOW ANSWER
Correct Ans:access-list 10 deny 172.16.144.0 0.0.7.255
Explanation:
First, you must know that a /21 is 255.255.248.0, which is a block size of 8 in the third octet. Counting by eight, this makes our subnet 144 in the third octet, and the wildcard for the third octet would be 7 since the wildcard is always one less than the block size.


2. You have created a named access list called Blocksales. Which of the following is a valid command for applying this to packets trying to enter interface s0 of your router?



SHOW ANSWER
Correct Ans:(config-if)# ip access-group Blocksales in
Explanation:
Using a named access list just replaces the number used when applying the list to the router's interface. ip access-group Blocksales in is correct.


3. What router command allows you to determine whether an IP access list is enabled on a particular interface?



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Correct Ans:show ip interface
Explanation:
Only the show ip interface command will tell you which interfaces have access lists applied. show access-lists will not show you which interfaces have an access list applied.


4.
You want to create a standard access list that denies the subnet of the following host: 172.16.50.172/20. Which of the following would you start your list with?



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Correct Ans:access-list 10 deny 172.16.48.0 0.0.15.255
Explanation:
First, you must know that a /20 is 255.255.240.0, which is a block size of 16 in the third octet. Counting by 16s, this makes our subnet 48 in the third octet, and the wildcard for the third octet would be 15 since the wildcard is always one less than the block size.


5. What command will permit SMTP mail to only host 1.1.1.1?



SHOW ANSWER
Correct Ans:access-list 110 permit tcp any host 1.1.1.1 eq smtp
Explanation:
When trying to find the best answer to an access-list question, always check the access-list number and then the protocol. When filtering to an upper-layer protocol, you must use an extended list, numbers 100-199 and 2000-2699. Also, when you filter to an upper-layer protocol, you must use either tcp or udp in the protocol field. If it says ip in the protocol field, you cannot filter to an upper-layer protocol. SMTP uses TCP.


6. You are working on a router that has established privilege levels that restrict access to certain functions. You discover that you are not able to execute the command show running-configuration. How can you view and confirm the access lists that have been applied to the Ethernet 0 interface on your router?



SHOW ANSWER
Correct Ans:show ip interface Ethernet 0
Explanation:
The only command that shows which access lists have been applied to an interface is show ip interface Ethernet 0. The command show access-lists displays all configured access lists, and show ip access-lists displays all configured IP access lists, but neither command indicates whether the displayed access lists have been applied to an interface.


7. You need to create an access list that will prevent hosts in the network range of 192.168.160.0 to 192.168.191.0. Which of the following lists will you use?



SHOW ANSWER
Correct Ans:access-list 10 deny 192.168.160.0 0.0.31.255
Explanation:
The range of 192.168.160.0 to 192.168.191.0 is a block size of 32. The network address is 192.168.160.0 and the mask would be 255.255.224.0, which for an access list must be a wildcard format of 0.0.31.255. The 31 is used for a block size of 32. The wildcard is always one less than the block size.


8. Which of the following is an example of a standard IP access list?



SHOW ANSWER
Correct Ans:access-list 1 deny 172.16.10.1 0.0.0.0
Explanation:
Standard IP access lists use the numbers 1-99 and 1300-1999 and filter based on source IP address only. Option C is incorrect because the mask must be in wildcard format.


9. Which command would you use to apply an access list to a router interface?



SHOW ANSWER
Correct Ans:ip access-group 101 in
Explanation:
To apply an access list, the proper command is ip access-group 101 in.


10.
Which of the following is true regarding access lists applied to an interface?





SHOW ANSWER
Correct Ans:One access list may be configured, per direction, for each layer 3 protocol configured on an interface.
Explanation:
A Cisco router has rules regarding the placement of access lists on a router interface. You can place one access list per direction for each layer 3 protocol configured on an interface



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