Find below best DNS Interview Questions and Answers that will assist every IT professional in clearing their Windows Server interview with ease. Though the answers provided are for windows server 2003, but you can still use these for 2008 and 2012 servers as well.
1. What is DNS?
DNS stands for Domain Name System. It is a hierarchical system for identifying hosts on the Internet or on a private, corporate TCP/IP internetwork.
It resolves the IP addresses to host names (or friendly internet names) and Host names to IP addresses.
2. What is the structure of DNS?
The structure of DNS starts with root domain. Then it (root domain) braches to TOP level domains, then second level domains, and so on to the individual host names.
Root Domain –> Top level Domains–> Second level Domains–> So on so forth up to individual host systems
3. How to install DNS?
We can install DNS in 3 different ways:
- While installing Operating System: While installing Operating System, It asks at Network Settings whether you want Typical settings or Custom Settings. Select Custom Settings–>Select Network Services–>click on Details–>Select DNS–>ok
- While installing through Active Directory (DCPROMO): (During installation it asks for CD)
- Independently: Programs –>Settings –>Control Panel –Add/Remove Programs –>Add/Remove Windows Components –>Select the Network Services–>Click on properties –>Select DNS –>OK (During the installation it asks for CD)
4. How to open DNS?
Start–>Run –>cmd –>dnsmgmt.msc
5. How to configure the DNS?
Open the DNS Console. Then you will find there
- Server name
- Forward Lookup Zone
- Reverse Lookup Zone
Note: If you have selected create automatically zones during the setup, then it creates the root zone and domain zone under forward lookup zone.
If no zones are there under forward lookup zone first create root zone then create domain zone.
6. What tabs are there on properties of Domain?
Domain properties contain the following tabs:
- Start of Authority (SOA)
- Named servers
- Zone transfers
7. What tabs are there on properties of Sever?
Server properties contain the following tabs:
- Root hints
8. Where to create the primary, secondary, Active Directory integrated zones?
If you want to create an Active Directory integrated zone, the server must be Domain Controller.
If you want to create the Primary DNS, you can create on Domain Controller or Member server. But if create on member you could not get 4 options under the domain which are meant for Active directory.
You can create Secondary zone on a Member Server or on a Domain Controller. There is no difference between them.
9. What commands do we use for DNS?
We use the following commands for DNS:
- Nslookup (and all interactive mode commands)
- Ipconfig /fulshdns
- Ipconfig /registerdns
10. What is the purpose of forward lookup?
Forward lookup resolves the Host names (Friendly Name) to IP addresses.
11. What is the purpose of Reverse lookup zone?
Reverse lookup resolves the IP addresses to Host names.
12. What is the difference between Primary zone and Secondary zone?
Primary zone has read and write permissions, whereas Secondary zone has read only permission.
Secondary zone is used for Backup and Load balancing.
13. How to check whether DNS is working or not?
In order to check whether a DNS is working or not, type the command “nslookup” in command prompt. It will give the DNS server name and its IP address
14. What is Dynamic Updates in DNS?
Generally we need to create a host record for newly joined computer (either client or Member server or Domain controller). If you enable dynamic Update option, then DNS itself creates associated host record for newly joined computers.
15. How to get Dynamic Update option?
Right Click on any zone –>properties –>on General tab u will get
Allow Dynamic Updates? [_Yes/No/Secure Updates]
Note: Put always Dynamic Updates “YES”
Note: If it is Active Directory Integrated zone you will get above three options.
But if it is Primary or Secondary zone you will get only “YES/NO” (You won’t get secure updates)
16. What is name Resolution?
The process of translating the name into some object or information that the name represents is called name resolution. A telephone book forms a namespace in which the names of telephone subscribers can be resolved to the phone numbers.
17. What is a zone?
Also called a zone of authority, zone is a subset of the Domain Name System (DNS) namespace that is managed by a name server.
A database of records is called a zone.
18. What is an iterative query?
The query that has been sent to the DNS server from a Client is called iterative query.
(i. e., iterative query is nothing but gives the answer for my question, don’t ask to contact that person or this person or don’t say something else. Simply just answer to my question. That’s all)
19. What is Recursive query?
Your DNS server requests the root level DNS server for specific IP address. Now DNS server says I don’t know but I can give the address other person who can help you in finding IP address.
20. What type of records do we find in DNS database?
The most general records found in DNS database are
- Host Record (A record)
- Mail Exchange Record (MX record)
- Canonical name or CNAME record (CNAME)
21. What is PTR record?
PTR record is created in Reverse lookup zone. It is the record to main database for reverse lookup zone purposes (to convert from IP address to host names). Each host record in forward lookup should have an associated pointer record in reverse lookup zone.
Generally first you will create a Forward lookup zone. Then go for Reverse lookup zone. Now we have to create associated pointer records for host records in forward lookup zone. If you are creating a host record in forward lookup zone after creating reverse lookup zone then here we need not to create a pointer record by coming to reverse lookup zone. When creating new host, click on the check box of create associated pointer record. Then it automatically creates associated pointer record in reverse lookup zone.
22. Is there any possibility to have two Primary DNS zones?
No, we cannot have two primary DNS zones. Why because if u have two primary DNS zones some clients contacts first one, some clients contacts second one according to their configuration in TCP/IP properties. Then you will get problems. Actually Primary DNS zone means Single master. i.e., master is only one that is only one primary DNS zone. But you can have as many as Secondary zones.
To overcome from above problem (i.e., single master problem) in Windows 2000 we have Active Directory Integrated zones, which are multi masters.
23. What is the default time setting in primary zone to Refresh, Retry, Expire intervals for secondary zone?
The default settings are
- To Refresh interval 10 minutes
- To Retry interval, 15 minutes
- To Expire after 1 day
24. Suppose the Secondary zone is Expired; now how to solve the problem?
First go to primary zone check primary zone is working or not.
IF primary zone is working then go to secondary zone, Right click on zone name select the “Transfer from Master” then it automatically contacts the primary DNS, if any updates are there then it takes the updates from the Primary.
25. How to know whether the recent changes in Primary zone are updated to secondary zone or not?
Compare the Serial Number on Start of Authority tab in both secondary on primary DNS zone properties.
If both are same then recent updates are made to secondary zone.
If not (i.e., secondary is less then primary) click on “Transfer from Master”
26. How to pause the zone?
- Click on the Pause button.
- Click on General tab
- Go to properties of a zone
Note: When you install a Windows 2000 DNS server, you immediately get all of the records of root DNS servers. So every windows 2000 DNS server installed on Internet has pre configured with the address of root DNS servers. So every single DNS server in the Internet can get root servers.
27. What is a forwarder?
(Open DNS console ==> Right click on Domain name ==> Click on forwarder tab)
A forwarder is server, which has more access than the present DNS server. May be our present DNS server is located in internal network and it cannot resolve the Internet names. Maybe it is behind a firewall or maybe it is using a proxy server or NAT server to get to the Internet. Then this server forwards the query to another DNS server that can resolve the Internet names.
Command prompt commands:
- Type Nslookup to get into the Nslookup mode.
- Type set type=SOA then press enter type domain name
- Type set type=NS then press enter; and type domain name.
- Type set type=ALL then press enter.
Note: To come out from Nslookup mode type exit.
28. What is name resolution?
Name resolution is nothing but the process of mapping a name to its corresponding IP address.
29. When developing naming strategy, which DNS server should we use?
Microsoft suggests that we use Windows 2000 DNS server. If you want to get 100% functionality you have to use 2000 DNS server. But you can also use BIND (Berkeley internet name domain) DNS servers, but if you want you use with Windows 2000 you should have at least Bind version 4.9.7. (Previous versions don’t support SRV records)
30. What is caching only DNS server?
Just install the DNS service into your windows 2000 server. Then it is called caching only DNS server, because it starts working for your clients to resolve the Internet names to IP address.
When you are installing DNS service at that time it is preconfigured with root DNS servers IP addresses.
If anybody wants to resolve the records that belong to your domain then you need to configure your DNS server appropriately.
31. Suppose under the forward lookup zone _msdcs, _tcp, _upd, _sites are not there (or you have deleted unexpectedly). How to get them back?
To get them back, simply just stop and start the netlogon service.
Type the following commands to stop and start the net logon service.
- Net stop netlogon
- Net start netlogon
Whenever you create a root zone (i.e., “.”) in a DNS server, the forwards, and root hints tabs will be disabled on that DNS server.