DNS Server Interview Questions And Answers

[Nimy]

1. What is BIND ?
BIND stands for Berkeley Internet Name Domain which is the most commonly used Domain Name System (DNS) server on the Internet.

2. What is the role of DNS ?
A DNS server, or name server, is used to resolve an IP address to a hostname or vice versa.

3. What is round robin DNS?
Round robin DNS is usually used for balancing the load of geographically distributed Web servers. For example, a company has one domain name and three identical home pages residing on three servers with three different IP addresses. When one user accesses the home page it will be sent to the first IP address. The second user who accesses the home page will be sent to the next IP address, and the third user will be sent to the third IP address. In each case, once the IP address is given out, it goes to the end of the list. The fourth user, therefore, will be sent to the first IP address, and so forth. 

4.What is Name Server?
A name server keeps information for the translation of domain names to IP addresses   and IP addresses to domain names. The name server is a program that performs the translation at the request of a resolver or another name server.

5. Explain "TTL"? 
Time To Live. A 32-bit number indicating the time the particular RR can be kept valid in a server cache. When this time expires, the record has to be considered invalid. The value 0 keeps nonauthoritative servers from saving the RR to their cache memory.

6. What is the role of "named-checkconf Utility"?
The named-checkconf utility checks the syntax of the named.conf configuration file.
Syntax: named-checkconf    [-t directory] [filename] 

7. What is the role of "named-checkzone Utility"?
The named-checkzone utility checks the syntax and consistency of the zone file.
Syntax:     named-checkzone [-dgv]   [-c class] zone   [filename]

[SIbinPhilip]

Hi,

Could you provide some more questions and answers about DNS.

[Vipin]

Hello Sibin,

I have got some DNS related questions and answers which I hope will help....

1. Who Defines TTL Value ?
Ans :- DNS Server

2. What is a Non-Autorative Server ?
Ans : Non authoritative servers do not contain copies of any domains. Instead they have a cache file that is constructed from all the DNS lookups it has performed in the past for which it has gotten an authoritative response. When a non-authoritative server queries an authoritative server and receives an authoritative answer, it passes that answer along to the querier as an authoritative answer. Thus, non-authoritative servers can answer authoritatively for a given resolution request. However, non-authoritative servers are not authoritative for any domain they do not contain specific zone files for. Most often, a non-authoritative server answers with a previous lookup from its lookup cache. Any answer retrieved from the cache of any server is deemed non-authoritative because it did not come from an authoritative server.

3. What is SOA ?
Ans :- The SOA record stores information about the name of the server that supplied the data for the zone;
the administrator of the zone; the current version of the data file; the number of seconds a secondary
name server should wait before checking for updates; the number of seconds a secondary name server should
wait before retrying a failed zone transfer; the maximum number of seconds that a secondary name server can
use data before it must either be refreshed or expire; and a default number of seconds for the time-to-live file
on resource records.

4. What are the types of RR (Resource Records) ?
Ans :- NS, A,Cname,SOA,DNAME,MX,SRV,TXT

5. Is ARPA a TLD ?
Ans:- Yes

6. How to check the content of Cache in Caching server ?
Ans :- rndc dumpdb -all
The above command will save all the cached data in a file named_dump.db in the var folder in Bind’s Home directory

7. What is the entire content of the zone file Called ?
Ans :- AXFR Record

8. How to Modify Zone Data Without Restarting the Name Server ?
Ans :- # rndc reload domain-name-of-zone
For BIND 8, run:
# ndc reload domain-name-of-zone
If you’ve modified multiple zones, just list them after reload. For example:
# rndc reload foo.example bar.example

9. What are the Types of DNS Sever’s
Ans :-
Split DNS
Cache DNS
Forward DNS
Stub DNS
Stealth DNS ———–Same As Split DNS
Recursive DNS

10. What are the Types Of Zone’s ?
Ans:-
Master
Slave
hint
forward
stub

[SIbinPhilip]

Hi Vipin,

Thank you for providing the question and answers. It really was helpful...

[Emanuelea]

Hi, Mark:
The related possible questions in the answer section are really good, but there are no answers provided, and some of those related questions are equally hard and tricky. Since there is a high chance that the interviewer is going to task those related questions, will you provide answers to them?