DNS Services

NAME RESOLUTION

It is a process of Mapping name to IPaddress.

i.e when we give name of the computer,it shows the IP of that computer.

NAME RESOLUTION TECHNIQUES

1.BROADCASTING

2.LMHOST FILE

3.WINS

4.NBTCACHE

5.HOSTFILE

6.DNS

1.BROADCASTING Generates broadcast packets to resolve name to IPaddress.This technique will create unnecessary network traffic.

2.LMHost file manually the entries will be created for each and every computer with respective to

their name and Ipaddress.

Creating entries in lmhost :-

Run ncpa.cpl

Local Area Connection properties

Internet Protocol TCP / IP – Properties

Advanced – WINS Tab

Import lmhost.sam file from C:\windows\system32\drivers\etc - OK

Go to ETC folder open lmhost file from notepad

At the end of file create an entry

Ex : IP Address – Computer Name (192.168.1.1 com1)

Save the file try to resolve by NetBios name

Disadvantage: manually the Netbios enteries should be typed in each and every computer.it takes

more time.

3.WINS It is a name mapping service basically use to map Netbios name to numerical IP

Address. A centralized server will be configured by installing WINS service which contains

the database of NetBIOS names and IPaddresses

4.NBTcache WINS server has a cache called NBTcache.the recently resolved entries will

be present here.the resolution of cached entries are faster when requested from clients.

5.Host file It is a File Which contains IPaddress with FQDN names.

Creating enteries in Host file

C:\windows\system32\drivers\etc - OK

Go to ETC folder open host file from notepad

At the end of file create an entry

Ex : IP Address – FQDN name ( 10.0.0.1 www.rooman.net)

Save the file

DNS Services

5.DNS (Domain Naming System)

Domain naming system is hierarchical distributed database that contains the mapping

of DNS Domain name (FQDN) to IP Address.

www :- Host Name

mail :- CDC

rooman.net :- PDC

mail.rooman.net :-DNS Suffix

www.mail.rooman.net :- FQDN (Fully qualified Domain Name)

The Length of host name is 63 characters.

The length of FQDN is 256 Characters.

DNS is a foundation of the Internet naming scheme. DNS supports alpha numeric

names. DNS is design to solves issues that across when there was increase in the number of

host on the network traffic generate by the update process size of the host file.

The following characters are valid for DNS Names

A – Z

a – z

0 – 9

Hyphen (-)

Domain name spaces are Hierarchical searching of Domains. When the request is

transferring to the domain name space first it will find from root server then to top level

domain. Then second level domain then request will send to particular machine.

Installing DNS Server Service :

Server manager

Roles - add roles – DNS – Install - Finish

com org net

N/W Traders

South East West

Sales

Root Domain

Top Level Domains

Second Level Domains

Sub Domains

Host Server

DNS Services

DNS Query :-

A Query is a request for name resolution to a DNS Server. There are two types of

Queries

Receive and Interactive.

DNS Clients and DNS Servers both initiate a queries for name resolution

An authoritative DNS Server for the Namespace of the Query will either Check the

cache, check the zone and return the requested I P Address.

Return an authoritative “NO”

A non authoritative DNS Server for the namespace of the query will be either

Forward the irresolvable query to a specific query server called a forwarder

Use root hints to locate an answer for two query

Recursive Queries :- It is a query made to a DNS Server in which DNS clients asks the DNS

Server to provide complete answer to the Query

Cache only DNS Server : Caching is the process of temporarily storing recently accessed

information in a special memory sub system for quicker access.

Caching Table :

Host Name IP Address TTL

clientA.contoso.mst 192.168.8.44 28 Seconds

Configuring Root Hint

Note :-Root hint usescache.dns file from C:/windows/system32/dns/cache.dns

Client –A

192.168.8.44

Client -2

Recursive

Query

Client -1

DNS Services

Configuring Root Hint

In DNS Server run dnsmgmt.msc

Select property of computer name

Select root hint tab

Add – enter FQDN name & IP Address of root server

OK – OK

From DNS client – try to resolve the records of root server.

Forwarders :- A Forwarder is a DNS server designed by other internal DNS Servers to

forward queries for resolving external or offsite DNS Domain Names.

Configure Forwarders

In DNS Server run dnsmgmt.msc

Select property of computer name – select forwards tab

Enter the IP address of DNS Server or root server

Add – OK – OK

From DNS Client try to resolve the records of DNS Server & root servers

Clearing DNS Cache in Server Side

In DNS Server

Run dnsmgmt.msc

R/C o Computer name select clear cache.

DNS Zones

It is a container which holds the resource records in order to resolve the information

or a Zone is a portion of DNS Data base that contains the resource records with the owner

name that belongs to the contiguous portion of DNS Name space.

Resource Records :

It is a standard DNS Database structure contains information which is use to process

DNS queries, or It is a information use to resolve Host name to IP Address & vice versa.

The location of DNS Database is C:/windows/system32/DNS

Root

Hint Forwarder

IP 192.168.3.200

DNS Server

A root.com

DNS Server

B root.com DNS Client

IP 192.168.3.10

PDNS : 192.168.3.200

DNS Services

Different resource records

A – Address or host – Resolve a host name to an IP Address

PTR – Pints – Resolves a IP Address to a host name

SOA – Start of Authority – The First record in any zone file

SRV – Service – Resolves names of servers providing services

SOA Records :- Indicates who is the owner of Forward Zone

SRV Service Record :- This Record will identify by prefixed with under score which points

to services for the Active Directory

Ex : _tcp, _udp, _ldap, _Kerberos.

NS : Name Server :- Identifies the DNS Server for each zone

MX – Mail Exchange :- The mail server the request forward to mail server will be redirected

using this record

C name : Canonical or Alias Name – Resolves from a host name to a host name

Zone types :- Forward lookup zone & Reverse lookup zone

Forward Lookup Zone: - It is container which is use to resolve the name to IP Address.

Reverse Lookup Zone: - It is a container which holds the resource records which is use to

resolve IP to Name. Whether it may be a Forward or Reverse lookup zone the sub zone types

are primary zone, secondary zone and Stub Zone.

Primary Zone :- It is a zone type in forward or reverse in order to maintain the resource

record where the records are read, write, copy.

Secondary zone :- It is a copy of DNS Database from primary zone which is a Read only

Database

Creating Primary zone

Run dnsmgmt.msc

R/C on forward lookup zone – New zone – ext

Select Primary zone – uncheck store zone in A/D – Enter Zone name

Zone file – Dynamic update ( It is a process of updating the DNS Client information

automatically in the DNS Server

Allow only Secure Dynamic Updates – If the DNS Client is member

machine then the record of that computer will update in the DNS Server.

Allow both non secure & secure Dynamic Updates :- If DNS Client is a

member or workgroup machine then its information will be updated

automatically in the DNS Server

Don to allow Automatic updates :- Records of DNS Client must configure

manually.

DNS Services

Next – Finish

In DNS Client enter Ipconfig /register dns to register the client computer name into DNS

server.

Configuring Primary Zone I Reverse Lookup Zone

IN DNS Server Run dnsmgmt.msc

Expand computer Name – R/C on Reverse Lookup Zone

Select New Zone – Select zone type as primary zone – Enter network ID – Ecreate

zone file as ex 30.168.192 in – addr.arpa.dns – next

Select dynamic update – next – Finish

Ping –a 192.168.1.1

Creating Secondary Zone

Run dsa.msc

R/C on Forward lookup zone – select new zone

Select zone type as Secondary Zone – Next

Enter the same zone name of primary zone – Next

Enter the master DNS Server IP Address – Add – Next – Finish

Zone Transfer :-

It is a technique of copying the resource records from primary zone to secondary zone

Note :- There will be no Zone Transfer between two Primary zones.

Configuring Zone Transfer:-

From Primary zone Run dnsmgmt.msc

Expand Forward lookup zone – Select Property of Zone

Select zone Transfer Tab

Select allow zone transfer only to the Following server

Enter IP Address of Secondary zone – OK

From Secondary zone run dnsmgmt.msc – R/C on the zone select Transfer from

Master

Active Directory Integrated Zone

An Active Directory integrated zone is a DNS Zone stored inside the Active Directory

Database.

Advantages :-

Stores DNS Zone Data in Active Directory and is thus more secure.

Uses Active Directory replication instead of Zone Transfers

o Zone Replication is a process of updating the DNS Database during Active

Directory Replication

Allows only secure Dynamic Updates

Uses Multi-Master instead of single Master Structure

Zone replication interval is 5 minutes where as interval of zone transfer is 15 minutes

DNS Services

Zone Delegation:-

It is a process of creating the link from Primary Zone of Parent Domain to the Primary

Zone of Child Domain in order to Access the Resource records of Child Domain.

Stub Zone: - It is a process of linking from the primary zone of the Parent Domain to

Secondary Zone of Child Domain in order to access the resource records of Child Domain

even if the Primary Zone is not working.

Zone Delegation: - Configure the DNS Server as Above mentioned scenario.

From the Primary Zone of Parent:- In Domain – Run dnsmgmt.msc – Expand Forward Lookup zone

R/C on Zone Select New Delegation

Enter Delegated Domain name as mail

Add – Enter FQDN name & IP Address of Delegated Domain (Primary Zone of Child

Domain) – Add – OK – Finish

From the Parent Domain try to resolve the Child Domain Resource Records.

DNS

Clients

DNS

Clients

Yahoo.com

Com 1 A 1.1

Com 2 A 1.2

Com3 A 1.3

Com 4 A 1.4

mail.yahoo.com

Com 1 A 1.5

Com 2 A 1.6

Com3 A 1.65

Com 4 A 1.70

Yahoo.com

mail.yahoo.co

m

Trust

Zone

Delegation

DNS Services

Configuring Stub Zone:-

Configure Zone Delegation t Primary Zone of Parent domain

Run dnsmgmt.msc – Expand Forwarder lookup zone – Expand Zone

Select Delegated Domain - Select name server record

R/C – Select Properties – Add – Enter the FQDN & IP Address of Secondary Zone of

Child Domain – OK

Down the Primary zone of Secondary Domain

From Primary Zone of Parent domain try to resolve the record of Child Domain

Aging & Scavenging Parameters

Aging is the process that determines whether a state DNS resource record should be

removed from the DNS Database

Scavenging is the Process of cleaning and removing outdated or extinct names data

from the WINS Database

A Refresh attempt is the process of a computer requesting a refresh on its DNS

Record

Setting Aging & Savaging

In DNS Server Run dnsmgmt.msc

R/C on Zone – Properties

Aging – Select Scavenge state resource record

Ok – yes – OK

Run Manual

Run dnsmgmt.msc – R/C on Server

Scavenge State Resource record

Yes

7 Days 7 Days

No Refresh Interval

Time Stamped

Scavenge Refresh Interval

Jan 1 Jan 8

Aging