DNS
Server Interview Questions and Answers
Active directory interview questions
Q1.
What is the main purpose of a DNS server?
Ans:
DNS servers are used to resolve FQDN hostnames into IP addresses and vice
versa.
Q2.
What is the port no of dns ?
Ans:
53.
Q3.
What is a Forward Lookup?
Q4.
What is Reverse Lookup?
Ans:
It?s a file contains host names to IP mapping information.
Q5.
What is a Resource Record?
Ans:
It is a record provides the information about the resources available in the
N/W infrastructure
.
Q6.
What are the diff. DNS Roles?
Ans:
Standard Primary, Standard Secondary, & AD Integrated.
Q7.
What is a Zone?
Ans:
Zone is a sub tree of DNS database.
Q8.
What is DNS?
Ans:
Domain Name System is a service that can be installed on any windows server
operating system to resolve the Name to IPAddress and vice-versa. TCP/IP
networks, such as the Internet, use DNS to locate computers and services
through user-friendly names
Q9.
What is DDNS?
Ans:
Dynamic DNS or DDNS is a method of updating, in real time, a Domain Name System
to point to a changing IP address on the Internet. This is used to provide a
persistent domain name for a resource that may change location on the network.
Q10.
What are the resource records in DNS?
Ans:
• A
(Address) Maps a host name to an IP address. When a computer has multiple
adapter cards and IP addresses, it should have multiple address records.
• CNAME
(Canonical Name) Sets an alias for a host name. For example, using this record,
zeta.tvpress.com can have an alias as www.tvpress.com.
• MX
(Mail Exchange) Specifies a mail exchange server for the domain, which allows
mail to be delivered to the correct mail servers in the domain.
• NS
(Name Server) Specifies a name server for the domain, which allows DNS lookups
within various zones. Each primary and secondary name server should bedeclared
through this record.
• PTR
(Pointer) Creates a pointer that maps an IP address to a host name for reverse
lookups.
• SOA
(Start of Authority) Declares the host that is the most authoritative for the
zone and, as such, is the best source of DNS information for the zone. Each
zone file must have an SOA record (which is created automatically when you add
a zone).
Q11.
How do you manually create SRV records in DNS?
Ans:
This is on windows server go to run ---> dnsmgmt.msc rightclick on the zone
you want to add srv record to and choose "other new record" and
choose service location(srv).
Q12.
What is the main purpose of SRV records ?
Ans:
SRV records are used in locating hosts that provide certain network services.
Q13.
Before installing your first domain controller in the network, you installed a
DNS server and created a zone, naming it as you would name your AD domain. However,
after the installation of the domain controller, you are unable to locate
infrastructure SRV records anywhere in the zone. What is the most likely cause
of this failure ?
Ans:
The zone you created was not configured to allow dynamic updates. The local
interface on the DNS server was not configured to allow dynamic updates.
Q14.
Which of the following conditions must be satisfied to configure dynamic DNS
updates for legacy clients ?
Ans:
The zone to be used for dynamic updates must be configured to allow dynamic
updates. The DHCP server must support, and be configured to allow, dynamic
updates for legacy clients.
Q15. At some point during the name
resolution process, the requesting party received authoritative reply. Which
further actions are likely to be taken after this reply ?
Ans:
After receiving the authoritative reply, the resolution process is effectively
over.
Q16.
What are a Forward and Reverse Lookup?
Ans:
• Forward
Lookup: When a name query is send to the DNS server against to IP address, it
is generally said a forward lookup.
• Reverse
Lookup: DNS also provides a reverse lookup process, enabling clients to use a
known IP address during a name query and look up a computer name based on its
address.
Q17.
What is Primary zone?
Ans:
This is the read and writable copy of a zone file in the DNS namespace. This is
primary source for information about the zone and it stores the master copy of
zone data in a local file or in AD DS. Dy default the primary zone file is
named as zone_name.dns in %windir%System32DNS folder on the server.
Q18.
What id Secondary zone?
Ans:
This is the read only copy of a zone file in the DNS namespace. This is
secondary source for information about the zone and it get the updated
information from the master copy of primary zone. The network access must be
available to connect with primary server. As secondary zone is merely a copy of
a primary zone that is hosted on another server, it cannot be stored in AD DS.
Q19.
What is stub Zone?
Ans:
A stub zone is a read only copy of a zone that contains only those resource
records which are necessary to identify the authoritative DNS servers for that
particular zone. A stub zone is practically used to resolve names between
separate DNS namespaces. This type of zone is generally created when a
corporate merger or acquire and DNS servers for two separate DNS namespaces
resolve names for clients in both namespaces.
A stub zone contains:
The start of authority (SOA) resource record, name
server (NS) resource records, and the glue A resource records for the delegated
zone.
The IP address of one or more master servers that
can be used to update the stub zone.
Secure services in your network require reverse name
resolution to make it more difficult to launch successful attacks against the services.
To set this up, you configure a reverse lookup zone and proceed to add records.
Which record types do you need to create?
Q20.
SOA records must be included in every zone. What are they used for ?
Ans:
SOA records contain a TTL value, used by default in all resource records in the
zone. SOA records contain the e-mail address of the person who is responsible
for maintaining the zone. SOA records contain the current serial number of the
zone, which is used in zone transfers.
Q21.
By default, if the name is not found in the cache or local hosts file, what is
the first step the client takes to resolve the FQDN name into an IP address ?
Ans:
Performs a recursive search through the primary DNS server based on the network
interface configuration .
Q22.
What is Caching Only Server?
Ans:
Caching-only servers are those DNS servers that only perform name resolution
queries, cache the answers, and return the results to the client. Once the
query is stored in cache, next time the query in resolved locally from cached
instead of going to the actual site.
Q23.
What is Aging and Scavenging?
Ans:
DNS servers running Windows Server support aging and scavenging features. These
features are provided as a mechanism to perform cleanup and removal of stale
resource records from the server and zone. This feature removes the dynamically
created records when they are stamped as stale.
By default, the aging and scavenging mechanism for
the DNS Server service is disabled.
Scavenging and aging must be enabled both at the DNS
server and on the zone
Q24.
What is SRV record in DNS?
Ans:
The SRV record is a resource record in DNS that is used to identify or point to
a computer that host specific services i.e Active directory.
Q25.
What is Forwarding in DNS?
Ans:
A forwarder is a feature in DNS server that is used to forward DNS queries for
external DNS names to DNS servers outside of that network. We ca configure a
DNS server as a forwarder to forward the name query to other DNS servers in the
network when they cannot resolve locally to that DNS server.
Q26.
What is Conditional Forwarding in DNS?
Ans:
We can configure the DNS server to forward queries according to specific domain
names using conditional forwarders. In this case query is forward to an IP
address against a DNS domain name.
Q27.
What does a zone consist of & why do we require a zone?
Ans:
Zone consists of resource records and we require zone for representing sites.
Q28.
What is Caching Only Server?
Ans:
When we install 2000 & 2003 server it is configured as caching only server
where it maintains the frequently accessed sites information and again when we
access the same site for next time it is obtain from cached information instead
of going to the actual site.
Q29.
What is forwarder?
Ans:
When one DNS server can?t receive the query it can be forwarded to another DNS
once configured as forwarder.
Q30.
What is secondary DNS Server?
Ans:
It is backup for primary DNS where it maintains a read only copy of DNS
database.
Q31.
How to enable Dynamic updates in DNS?
Ans:
Start>Program>Admin tools> DNS >Zone properties.
Q32.
What are the properties of DNS server?
Ans:
INTERFACES, FORWARDERS, ADVANCED, ROUTINGS, SECURITY, MONITORING, LOGGING,
DEBUG LOGGING.
Q33.
Properties of a Zone ?
Ans:
General, SOA, NAMESERVER, WINS, Security, and ZONE Transfer.
Q34.
What is scavenging?
Ans:
Finding and deleting unwanted records.
Q35.
What are SRV records?
Ans:
SRV are the service records, there are 6 service records. They are useful for
locating the services.
Q36.
What are the types of SRV records?
Ans:
MSDCS:Contains DCs information.
TCP:Contains Global Catalog, Kerberos & LDAP
information.
UDP:Contains Sites information.
Sites:Contains Sites information.
Domain DNS Zone:Conations domain?s DNS specific
information.
Forest DNS zone:Contains Forest?s Specific
Information.
Q37.
Where does a Host File Reside?
Ans:
c:\windows\system32\drivers\etc.
Q38.
What is SOA?
Ans:
Start of Authority: useful when a zone starts. Provides the zone startup
information.
Q39.
What is a query?
Ans:
A request made by the DNS client to provide the name server information.
Q40.
What are the diff. types of Queries?
Ans:
Recursion, iteration.
Q41.
Tools for troubleshooting DNS?
Ans:
DNS Console, NSLOOKUP, DNSCMD, IPCONFIG, Logs.
Q42.
What is WINS server? where we use WINS server? difference between DNS and WINS?
Ans:
WINS is windows internet name service used to resolve the NetBIOS(computer
name)name to IP address.This is proprietary for Windows.You can use in LAN.DNS
is a Domain Naming System, which resolves Host names to IP addresses. It uses
fully qualified domain names. DNS is an Internet standard used to resolve host
names.
Q42.
What is new in Windows Server 2003 regarding the DNS management?
Ans:
When DC promotion occurs with an existing forest, the Active Directory
Installation Wizard contacts an existing DC to update the directory and
replicate from the DC the required portions of the directory.
If the wizard fails to locate a DC, it performs
debugging and reports what caused the failure and how to fix the problem. In
order to be located on a network, every DC must register in DNS DC locator DNS
records. The Active Directory Installation Wizard verifies a proper
configuration of the DNS infrastructure. All DNS configuration debugging and
reporting activity is done with the Active Directory Installation Wizard.
Q43.
SOA records must be included in every zone. What are they used for?
Ans:
SOA records contain a TTL value, used by default in all resource records in the
zone. SOA records contain the e-mail address of the person who is responsible
for maintaining the zone. SOA records contain the current serial number of the
zone, which is used in zone transfers.
By default, if the name is not found in the cache or
local hosts file, what is the first step the client takes to resolve the FQDN
name into an IP address? Performs a recursive search through the primary DNS
server based on the network interface configuration.
Q44.
How do I clear the DNS cache on the DNS server?
Ans:
Go to cmd prompt and type ipconfig /flushdns .
Q45.
What is the main purpose of SRV records?
Ans:
SRV records are used in locating hosts that provide certain network services.
Q46.
Before installing your first domain controller in the network, you installed a
DNS server and created a zone, naming it as you would name your AD domain.
However, after the installation of the domain controller, you are unable to
locate infrastructure SRV records anywhere in the zone. What is the most likely
cause of this failure?
Ans:
The zone you created was not configured to allow dynamic updates. The local
interface on the DNS server was not configured to allow dynamic updates.
Q47.
What is the "." zone in my forward lookup zone?
Ans:
This setting designates the Windows 2000 or Windows Server 2003 DNS server to be
a root hint server and is usually deleted. If you do not delete this setting,
you may not be able to perform external name resolution to the root hint
servers on the Internet.
Q48.
Do I need to configure forwarders in DNS?
Ans:
No. By default, Windows 2000 DNS uses the root hint servers on the Internet;
however, you can configure forwarders to send DNS queries directly to your
ISP's DNS server or other DNS servers. Most of the time, when you configure
forwarders, DNS performance and efficiency increases, but this configuration
can also introduce a point of failure if the forwarding DNS server is
experiencing problems.
The root hint server can provide a level of
redundancy in exchange for slightly increased DNS traffic on your Internet
connection. Windows Server 2003 DNS will query root hints servers if it cannot
query the forwarders.
Q49.
Should I point the other Windows 2000-based and Windows Server 2003-based
computers on my LAN to my ISP's DNS servers?
Ans:
No. If a Windows 2000-based or Windows Server 2003-based server or workstation
does not find the domain controller in DNS, you may experience issues joining
the domain or logging on to the domain. A Windows 2000-based or Windows Server
2003-based computer's preferred DNS setting should point to the Windows 2000 or
Windows Server 2003 domain controller running DNS.
If you are using DHCP, make sure that you view scope
option #15 for the correct DNS server settings for your LAN.
Q50.
Do I need to point computers that are running Windows NT 4.0 or Microsoft
Windows 95, Microsoft Windows 98, or Microsoft Windows 98 Second Edition to the
Windows 2000 or Windows Server 2003 DNS server?
Ans:
Legacy operating systems continue to use NetBIOS for name resolution to find a
domain controller; however it is recommended that you point all computers to
the Windows 2000 or Windows Server 2003 DNS server for name resolution.
Q51.
What if my Windows 2000 or Windows Server 2003 DNS server is behind a proxy
server or firewall?
Ans:
If you are able to query the ISP's DNS servers from behind the proxy server or
firewall, Windows 2000 and Windows Server 2003 DNS server is able to query the
root hint servers. UDP and TCP Port 53 should be open on the proxy server or
firewall.
Q52.
What should I do if the domain controller points to itself for DNS, but the SRV
records still do not appear in the zone?
Ans:
Check for a disjointed namespace, and then run Netdiag.exe /fix.
You must install Support Tools from the Windows 2000
Server or Windows Server 2003 CD-ROM to run Netdiag.exe.
Q53.
How do I set up DNS for a child domain?
Ans:
To set up DNS for a child domain, create a delegation record on the parent DNS
server for the child DNS server. Create a secondary zone on the child DNS
server that transfers the parent zone from the parent DNS server.
Note Windows Server 2003 has additional types of
zones, such as Stub Zones and forest-level integrated Active Directory zones,
that may be a better fit for your environment. Set the child domain controller
to point to itself first. As soon as an additional domain controller is
available, set the child domain controller to point to this domain controller
in the child domain as its secondary.
Q54.
What are Queries types in DNS?
Ans:
• Recursive
Query: This name queries are generally made by a DNS client to a DNS server or
by a DNS server that is configured to pass unresolved name queries to another
DNS server, in the case of a DNS server configured to use a forwarder.
• Iterative
Query: An iterative name query is one in which a DNS client allows the DNS
server to return the best answer it can give based on its cache or zone data.
If the queried DNS server does not have an exact match for the queried name,
the best possible information it can return is a referral. The DNS client can
then query the DNS server for which it obtained a referral. It continues this
process until it locates a DNS server that is authoritative for the queried
name, or until an error or time-out condition is met.
Q55.
What are Tools for troubleshooting of DNS?
Ans:
DNS Console, NSLOOKUP, DNSCMD, IPCONFIG, DNS Logs.
Q56.
How to check DNS health?
Ans:
Using the DCdiag.
i.e. (dcdiag /test:dns /v /e)
.....Best Of Luck.....
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