DNS Records Commonly Used Records

Commonly used Record Types

The most commonly used record types are: A, CNAME, MX, NS, PTR and SOA.

A-Records (Host address)

• The A-record is the most basic and the most important DNS record type.

• They are used to translate human friendly domain names such as “www.jhsoft.com” into IP-addresses such as 23.211.43.53 (machine friendly numbers).

• A-records are the DNS server equivalent of the hosts file – a simple domain name to IP-address mapping.

• A-records are not required for all computers, but is needed for any computer that shares resources on a network.

• This record type is defined in RFC1035.

CNAME-Records (Canonical name for an alias)

CNAME-records are domain name aliases.

• Often computers on the Internet have multiple functions such as web-server, ftp-server, chat-server etc.

• To mask this, CNAME-records can be used to give a single computer multiple names (aliases).

• For example computer “xyz.com” may be both a web-server and an ftp-server, so two CNAME-records are defined:

• “www.xyz.com” = “xyz.com” and “ftp.xyz.com” = “xyz.com”.

• Sometimes a single server computer hosts many different domain names (take ISPs), and so CNAME-records may be defined such as “www.abc.com” =

• “www.xyz.com”.

• The most popular use the CNAME-record type is to provide access to a web-server using both the standard “www.domain.com” and “domain.com” (without the

• www).

• This is usually done by creating an A-record for the short name (without www), and a CNAME-record for the www name pointing to the short name.

• CNAME-records can also be used when a computer or service needs to be renamed, to temporarily allow access through both the old and new name.

• A CNAME-record should always point to an A-record to avoid circular references.

• This record type is defined in RFC1035.

MX-Records (Mail exchange)

MX-records identify mail server(s) responsible for a domain name.

• When sending an e-mail to “user@xyz.com”, your mail server must first look up the MX-record for “xyz.com” to see which mail server actually handles mail for

• “xyz.com” (this could be “mail.xyz.com” – or someone else’s mail server like “mail.isp.com”).

• Then it looks up the A-record for the mail server to connect to its IP-address.

• An MX-record has a “Preference” number indicating the order in which the mail server should be used.

• (Only relevant when multiple MX-records are defined for the same domain name).

• Mail servers will attempt to deliver mail to the server with the lowest preference number first, and if unsuccessful continue with the next lowest and so on.

• An MX-record identifies the name of a mail server server – not the IP-address.

• Because of this, it is important that an A-record for the referenced mail server exists (not necessarily on your server, but wherever it belongs), otherwise there may

• not be any way to find that mail server and communicate with it.

• Do not point an MX record to a CNAME-record. Many e-mail servers don’t handle this. Add another A-record instead.

• This record type is defined in RFC1035.

NS-Records (Authoritative name server)

NS-records identify DNS servers responsible (authoritative) for a zone.

• A zone should contain one NS-record for each of its own DNS servers (primary and secondaries).

• This mostly is used for zone transfer purposes (notify).

• These NS-records have the same name as the zone in which they are located.

• But the most important function of the NS-record is delegation.

• Delegation means that part of a domain is delegated to other DNS servers.

• For example all “.com” sub-names (such as “jhsoft.com”) are delegated from the “com” zone (hosted by the “InterNic”).

• The “com” zone contains NS-records for all “.com” sub-names (a lot!).

• You can also delegate sub-names of your own domain name (such as “subname.yourname.com”) to other DNS servers.

• You are in effect the “InterNic” for all sub-names of your own domain name (if you have a really cool domain name, you might even be able to sell sub-names for

• profit).

• To delegate “subname.yourname.com”, create NS-records for “subname.yourname.com” in the “yourname.com” zone.

• These NS-records must point to the DNS server responsible for “subname.yourname.com” for example “ns1.subname.yourname.com” – or a DNS server

• somewhere else like “ns1.othername.net”.

• An NS-record identifies the name of a DNS server – not the IP-address.

• Because of this, it is important that an A-record for the referenced DNS server exists (not necessarily on your server, but wherever it belongs), otherwise there may

• not be any way to find that DNS server and communicate with it.

• If an NS-record delegates a sub-name (“subname.yourname.com”) to a DNS server with a name in that sub-name (“ns1.subname.yourname.com”), an A-record for

• that server (“”ns1.subname.yourname.com”) must exist in the parent zone (“yourname.com”).

• This A-record is referred to as a “glue” record, because it doesn’t really belong in the parent zone, but is necessary to locate the DNS server for the delegated

• sub-name.

• This record type is defined in RFC1035.

PTR-Records (domain name pointer)

PTR-records map IP addresses to domain names (reverse of A-records).

• A PTR-record’s name is the IP address written in backward order with “in-addr.arpa.” appended to the end.

• As an example, looking up the domain name for IP address “1.2.3.4″ is done through a query for the PTR-record for “4.3.2.1.in-addr.arpa.”

• This record type is defined in RFC1035.

SOA-Records (Start of authority)

Each zone contains exactly one SOA-record, which holds the following properties for the zone:

• Name of primary DNS server

• The domain name of the primary DNS server for the zone.

• The zone should contain a matching NS-record.

• Mailbox of responsible person

• The email address (replace @ with a dot) of the person responsible for maintenance of the zone.

• The standard for this is the “hostmaster” username – such as “hostmaster.jhsoft.com” (= hostmaster@jhsoft.com).

• Serial number (Zone Transfers)

• Used by secondary DNS servers to check if the zone has changed.

• If the serial number is higher than what the secondary server has, a zone transfer will be initiated.

• Refresh Interval (see Zone Transfers)

• How often secondary DNS servers should check if changes are made to the zone.

• Retry Interval (see Zone Transfers)

• How often secondary DNS server should retry checking if changes are made – if the first refresh fails.

• Expire Interval (see Zone Transfers)

• How long the zone will be valid after a refresh.

• Secondary servers will discard the zone if no refresh could be made within this interval.

• Minimum (default) TTL

• Used as the default TTL for new records created within the zone.

• Also used by other DNS server to cache negative responses (such as record does not exist etc.).

• This record type is defined in RFC1035.

Less commonly used / experimental record types

The following are all less commonly used / experimental record types.

A6-Records (IPv6 host address)

• IPv6 is the future replacement for the current IP address system (also known as IPv4).

• The current IPv4 addresses are 32 bits long ( x . x . x . x = 4 bytes), and therefore “only” support a total of 4,294,967,296 addresses – less than the global

• population.

• With this limitation there is an increasing shortage of IPv4 addresses.

• To solve the problem, the whole Internet will eventually be migrated to IPv6.

• IPv6 addresses are 128 bits long and and are written in hexadecimal numbers separated by colons (:) at every four digits.

• Zeros can be skipped – for example: 4C2F::1:2:3:4:567:89AB.

• Few applications and network devices currently support IPv6 and IPv6 addresses are not yet generally available., but this is expected to change rapidly.

• An A6-record is used to specify the IPv6 address (or part of the IPv6 address) for a host.

• A6-records expands the functionality of A- and AAAA-records by adding support for aggregation and renumbering.

• A lookup for an IPv6 records could involve several A6-records which each specify only part of the final address.

• This is achieved through the additional prefix-length and prefix name fields.

• A6-records are supposed to replace AAAA-records (see below).

• This record type is defined in RFC2874.

AAAA-Records (IPv6 host address)

• An AAAA-record specifies an absolute IPv6 address.

• This record type is supposed to be replaced by the A6 record type (see above).

• This record type is defined in RFC1886.

AFSDB-Records (AFS Data Base location)

• An AFSDB-record maps a domain name to an AFS (Andrew File System) database server.

• The server name points to an A-record for the database server, and the sub-type indicates server type:

1. AFS version 3.0 volume location server for the named AFS cell.

2. DCE authenticated server

• This record type is defined in RFC1183.

ATMA-Records (Asynchronous Transfer Mode address)

• An ATMA-record maps a domain name to an ATM address.

• The ATM address can be specified in either E.164 format (decimal) or NSAP format (hexadecimal).

• This record type is defined in “ATM Name System Specification Version 1.0″ published by the ATM Forum.

• DNAME-Records (Non-Terminal DNS Name Redirection)

• A DNAME-record is used to map / rename an entire subtree of the DNS name space to another domain.

• It differs from the CNAME-record which maps only a single node of the name space.

• This record type is defined in RFC2672.

HINFO-Records (Host information)

• A HINFO-record specifies the host / server’s type of CPU and operating system.

• This information can be used by application protocols such as FTP, which use special procedures when communicating with computers of a known CPU and

• operating system type.

• Standard CPU and operating system types are defined in RFC1700 (Page 206 / 214).

• The standard for a Windows PC is “INTEL-386″ / “WIN32″.

• This record type is defined in RFC1035.

ISDN-Records (ISDN address)

• The ISDN-record maps a domain name to an ISDN (Integrated Services Digital Network) telephone number.

• The ISDN phone numbers / DDI (Direct Dial In) used should follow ITU-T E.163/E.164 international telephone numbering standards.

• For example 12121234567 ( 1=USA, 212=New York area code, 1234567=number)

• The ISDN sub-address is an optional hexadecimal number.

• This record type is defined in RFC1183.

MB, MG, MINFO, MR Records (mailbox records)

• Most Internet mail servers only support MX-records.

• Only use MB, MG, MINFO and MR records if you have specific requirements for these.

• To specify “mailbox” names, replace the email address @ sign with a dot (.).

• MB-records (Mailbox)

• Maps a mailbox to a host (server).

• The host must be the same as a valid A-record already defined in the same zone.

• MG-records (Mail group member)

• Used to specify mail group members (one MG-record per member).

• Each member mailbox must be identical to a valid mailbox (MB-record).

• MINFO-records (Mailbox or mail list information)

• Specifies the mailbox of the responsible person and optionally a mailbox for errors for this mailbox or list.

• Each mailbox must be the same as a valid mailbox (MB-record) that already exist in the zone.

• MR-records (Renamed mailbox)

• Specifies a renamed mailbox.

• An MR-record can be used as a forwarding entry for a user who has moved to a different mailbox.

• These record types are defined in RFC1035.

NSAP-Records (NSAP address)

• An NSAP-record maps a domain name to an NSAP address.

• The NSAP address is entered using hexadecimal digits – any NSAP address format is allowed.

• This record type is defined in RFC1706.

RP-Records (Responsible person)

• An RP-record specifies the mailbox of the person responsible for the host (domain name).

• A SOA-record defines the responsible person for an entire zone, but a zone may contain a large number of individual hosts / domain names for which different

• people are assigned responsibility.

• The RP-record type makes it possible to identify the responsible person for individual domain names contained within the zone.

• To specify the “mailbox”, replace the email address @ sign with a dot (.).

• Optionally specify the domain name for a TXT-record with additional information (such as phone and address).

• This record type is defined in RFC1183.

RT-Records (Route through)

• An RT-record specifies an intermediate host that provides routing to the domain name (host) of the record.

• This can be used by computers which are not directly connected to the Internet, or wide area network (WAN).

• A preference value is used to set priority if multiple intermediate routing hosts are specified – lower values tried first.

• For each intermediate host specified, a corresponding host (A) address resource record is needed in the current zone.

• This record type is defined in RFC1183.

SRV-records (location of service)

• SRV-records are used to specify the location of a service.

• They are recently being used in connection with different directory servers such as LDAP (Lightweight Directory Access Protocol), and Windows 2000 directory

• services.

• They can also be used for advanced load balancing and to specify specific ports for services – for example that a web-server is running on port 8080 instead of the

• usual port 80.

• This record type is however still considered experimental, and is NOT supported by most programs in use today, including web-browsers.

• The name of a SRV-record is defined as “_service._protocol.domain” – for example “_ftp._tcp.xyz.com”.

• Most internet services are defined in RFC1700 (page 15), and the protocol is generally TCP or UDP.

• The “service location” is specified through a target, priority, weight, and port:

• - Target is the domain name of the server (referencing an A-record).

• - Priority is a preference number used when more servers are providing the same service (lower numbers are tried first).

• - Weight is used for advanced load balancing.

• - Port is the TCP/UDP port number on the server that provides this service.

• This record type is defined in RFC2782.

TXT-Records (Descriptive text)

• TXT-records are used to hold descriptive text.

• They are often used to hold general information about a domain name such as who is hosting it, contact person, phone numbers, etc.

• TXT-records are informational for people only and are not required for any DNS functions.

• This record type is defined in RFC1035.

X25-Records (X.25 PSDN address)

• An X25-records maps a domain name to a Public Switched Data Network (PSDN) address number.

• Numbers used with this record should follow the X.121 international numbering plan.

• This record type is defined in RFC1183.

WKS Records (Well Known Services)

• The Well Known Services (WKS) record lists the Well Known Services a host provides on a particular IP protocol. The common protocols are TCP and UDP.

• The common services are TIME, TELNET, FTP, or SMTP.

• This record type is defined in RFC1035.

system administrator interview question with answer Part -2

System administrator interview question with answer Part -2

What is the KCC
The KCC is a built-in process that runs on all domain controllers and generates replication topology for the Active Directory forest. The KCC creates separate replication topologies depending on whether replication is occurring within a site (intrasite) or between sites (intersite). The KCC also dynamically adjusts the topology to accommodate new domain controllers, domain controllers moved to and from sites, changing costs and schedules, and domain controllers that are temporarily unavailable.

How do you view replication properties for AD?
By using Active Directory Replication Monitor.
Start–> Run–> Replmon

What are sites What are they used for?
One or more well-connected (highly reliable and fast) TCP/IP subnets. A site allows administrators to configure Active Directory access and replication topology to take advantage of the physical network.

Name some OU design considerations?
OU design requires balancing requirements for delegating administrative rights – independent of Group Policy needs – and the need to scope the application of Group Policy. The following OU design recommendations address delegation and scope issues:
Applying Group Policy An OU is the lowest-level Active Directory container to which you can assign Group Policy settings. Delegating administrative authority usually don’t go more than 3 OU levels
http://technet.microsoft.com/en-us/library/cc783140.aspx

What are FMSO Roles? List them.
Fsmo roles are server roles in a Forest
There are five types of FSMO roles
1-Schema master
2-Domain naming master
3-Rid master
4-PDC Emullator
5-Infrastructure master

Logical Diagram of Active Directory ?, What is the difference between child domain & additional domain Server?
Well, if you know what a domain is then you have half the answer. Say you have the domain Microsoft.com. Now microsoft has a server named server1 in that domain, which happens to the be parent domain. So it’s FQDN is server1.microsoft.com. If you add an additional domain server and name it server2, then it’s FQDN is server2.microsoft.com.
Now Microsoft is big so it has offices in Europe and Asia. So they make child domains for them and their FQDN would look like this: europe.microsoft.com & asia.microsoft.com. Now lets say each of them have a server in those child domains named server1. Their FQDN would then look like this: server1.europe.microsoft.com & server1.asia.microsoft.com..

What are Active Directory Groups?
Groups are containers that contain user and computer objects within them as members. When security permissions are set for a group in the Access Control List on a resource, all members of that group receive those permissions. Domain Groups enable centralized administration in a domain. All domain groups are created on a domain controller.
In a domain, Active Directory provides support for different types of groups and group scopes. The group type determines the type of task that you manage with the group. The group scope determines whether the group can have members from multiple domains or a single domain.
Group Types
* Security groups: Use Security groups for granting permissions to gain access to resources. Sending an e-mail message to a group sends the message to all members of the group. Therefore security groups share the capabilities of distribution groups.
* Distribution groups: Distribution groups are used for sending e-main messages to groups of users. You cannot grant permissions to security groups. Even though security groups have all the capabilities of distribution groups, distribution groups still requires, because some applications can only read distribution groups.
Group Scopes
Group scope normally describe which type of users should be clubbed together in a way which is easy for there administration. Therefore, in domain, groups play an important part. One group can be a member of other group(s) which is normally known as Group nesting. One or more groups can be member of any group in the entire domain(s) within a forest.
* Domain Local Group: Use this scope to grant permissions to domain resources that are located in the same domain in which you created the domain local group. Domain local groups can exist in all mixed, native and interim functional level of domains and forests. Domain local group memberships are not limited as you can add members as user accounts, universal and global groups from any domain. Just to remember, nesting cannot be done in domain local group. A domain local group will not be a member of another Domain Local or any other groups in the same domain.
* Global Group: Users with similar function can be grouped under global scope and can be given permission to access a resource (like a printer or shared folder and files) available in local or another domain in same forest. To say in simple words, Global groups can be use to grant permissions to gain access to resources which are located in any domain but in a single forest as their memberships are limited. User accounts and global groups can be added only from the domain in which global group is created. Nesting is possible in Global groups within other groups as you can add a global group into another global group from any domain. Finally to provide permission to domain specific resources (like printers and published folder), they can be members of a Domain Local group. Global groups exist in all mixed, native and interim functional level of domains and forests.
* Universal Group Scope: these groups are precisely used for email distribution and can be granted access to resources in all trusted domain as these groups can only be used as a security principal (security group type) in a windows 2000 native or windows server 2003 domain functional level domain. Universal group memberships are not limited like global groups. All domain user accounts and groups can be a member of universal group. Universal groups can be nested under a global or Domain Local group in any domain.

What are the types of backup? Explain each?
Incremental
A “normal” incremental backup will only back up files that have been changed since the last backup of any type. This provides the quickest means of backup, since it only makes copies of files that have not yet been backed up. For instance, following our full backup on Friday, Monday’s tape will contain only those files changed since Friday. Tuesday’s tape contains only those files changed since Monday, and so on. The downside to this is obviously that in order to perform a full restore, you need to restore the last full backup first, followed by each of the subsequent incremental backups to the present day in the correct order. Should any one of these backup copies be damaged (particularly the full backup), the restore will be incomplete.
Differential
A cumulative backup of all changes made after the last full backup. The advantage to this is the quicker recovery time, requiring only a full backup and the latest differential backup to restore the system. The disadvantage is that for each day elapsed since the last full backup, more data needs to be backed up, especially if a majority of the data has been changed.

What is the SYSVOL folder?
The Windows Server 2003 System Volume (SYSVOL) is a collection of folders and reparse points in the file systems that exist on each domain controller in a domain. SYSVOL provides a standard location to store important elements of Group Policy objects (GPOs) and scripts so that the File Replication service (FRS) can distribute them to other domain controllers within that domain.
You can go to SYSVOL folder by typing : %systemroot%/sysvol

What is the ISTG Who has that role by default?
The first server in the site becomes the ISTG for the site, The domain controller holding this role may not necessarily also be a bridgehead server.

What is the order in which GPOs are applied?
Local, Site, Domain, OU

system administrator interview question with answers- Part 1

1. Can a workstation computer be configured to browse the Internet and yet NOT have a default gateway?
If we are using public ip address, we can browse the internet. If it is having an intranet address a gateway is needed as a router or firewall to communicate with internet.
2. What is CIDR?
CIDR (Classless Inter-Domain Routing, sometimes known as supernetting) is a way to allocate and specify the Internet addresses used in inter-domain routing more flexibly than with the original system of Internet Protocol (IP) address classes. As a result, the number of available Internet addresses has been greatly increased. CIDR is now the routing system used by virtually all gateway hosts on the Internet’s backbone network. The Internet’s regulating authorities now expect every Internet service provider (ISP) to use it for routing.
3. What is DHCP? What are the benefits and drawbacks of using it?
DHCP is Dynamic Host Configuration Protocol. In a networked environment it is a method to assign an ‘address’ to a computer when it boots up.
Advantages
All the IP configuration information gets automatically configured for your client machine by the DHCP server.
If you move your client machine to a different subnet, the client will send out its discover message at boot time and work as usual. However, when you first boot up there you will not be able to get back the IP address you had at your previous location regardless of how little time has passed.
Disadvantage
Your machine name does not change when you get a new IP address. The DNS (Domain Name System) name is associated with your IP address and therefore does change. This only presents a problem if other clients try to access your machine by its DNS name.
4. How do you manually create SRV records in DNS?
To create SRV records in DNS do below steps: -
Open DNS
Click on Zone —– Select domain abc.local ——-
Right Click to domain and go to Other New Records——
And choose service location (SRV)
5. Name 3 benefits of using AD-integrated zones?
Benefits as follows
a. you can give easy name resolution to ur clients.
b. By creating AD- integrated zone you can also trace hacker and spammer by creating reverse zone.
c. AD integrated zoned all for incremental zone transfers which on transfer changes and not the entire zone. This reduces zone transfer traffic.
d. AD Integrated zones suport both secure and dmanic updates.
e. AD integrated zones are stored as part of the active directory and support domain-wide or forest-wide replication through application pertitions in AD.
6. How do I clear the DNS cache on the DNS server?
Go to cmd prompt and type “ipconfig/flushdns” without quotes
7. What is NAT?
NAT (Network Address Translation) is a technique for preserving scarce Internet IP addresses. For more details go to Microsoft link
8. How do you configure NAT on Windows 2003?
For above answer go to below link
Configure NAT
9. How to configure special ports to allow inbound connections?
a. Click Start, Administrative Tools, and then click Routing and Remote Access to open the Routing and Remote Access management console.
b. Locate the interface that you want to configure.
c. Right-click the interface and then select Properties from the shortcut menu.
d. Click the Special Ports tab.
e. Under Protocol, select TCP or UDP and then click the Add button.
f. Enter the port number of the incoming traffic in Incoming Port.
g. Select On This Address Pool Entry, and provide the public IP address of the incoming traffic.
h. Enter the port number of the private network resource in Outgoing Port.
i. Enter the private network resource’s private IP address in Private Address.
j. Click OK.

Windows Server 2008 System / Network Administrator Questions with Answers -Part 3

What is DHCP’s purpose?
DHCP’s purpose is to enable individual computers on an IP network to extract their configurations from a server (the ‘DHCP server’) or servers, in particular, servers that have no exact information about the individual computers until they request the information. The overall purpose of this is to reduce the work necessary to administer a large IP network. The most significant piece of information distributed in this manner is the IP address.

What protocol and port does DHCP use?
DHCP, like BOOTP runs over UDP, utilizing ports 67 and 68.

What is Global Catalog? The Global Catalog authenticates network user logons and fields inquiries about objects across a forest or tree. Every domain has at least one GC that is hosted on a domain controller. In Windows 2000, there was typically one GC on every site in order to prevent user logon failures across the network.
What is Stub Zone in DNS Server?
A stub zone is a copy of a zone that contains only those resource records necessary to identify the authoritative Domain Name System (DNS) servers for that zone. A stub zone is used to resolve names between separate DNS namespaces. This type of resolution may be necessary when a corporate merger requires that the DNS servers for two separate DNS namespaces resolve names for clients in both namespaces.
A stub zone consists of:

• 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.

The master servers for a stub zone are one or more DNS servers authoritative for the child zone, usually the DNS server hosting the primary zone for the delegated domain name.
Where is the file of Active Directory data file stored?
Active Directory data store in %SystemRoot%\ntds\NTDS.DIT. The ntds.dit file is the heart of Active Directory including user accounts
What are the types of records in DNS?
To see the records of DNS Server checks this path - DNS Records
What is DHCP and at which port DHCP work?
Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers (i.e., a scope) configured for a given network. DHCP assigns an IP address when a system is started
DHCP client uses port 67 and the DHCP server uses port 68.
What is DORA process in DHCP and How it works?
DHCP (D)iscover
DHCP (O)ffer
DHCP (R)equest
DHCP (A)cknowledge
1) Client makes a UDP Broadcast to the server about the DHCP discovery.
2) DHCP offers to the client.
3) In response to the offer Client requests the server.
4) Server responds all the Ip Add/mask/gty/dns/wins info along with the acknowledgement packet.
What is Super Scope in DHCP?
A superscope allows a DHCP server to provide leases from more than one scope to clients on a single physical network. Before you can create a superscope, you must use DHCP Manager to define all scopes to be included in the superscope. Scopes added to a superscope are called member scopes. Superscopes can resolve DHCP service issues in several different ways; these issues include situations in which:

• Support is needed for DHCP clients on a single physical network segment—such as a single Ethernet LAN segment—where multiple logical IP networks are used. When more than one logical IP network is used on a physical network, these configurations are also known as multinets.
• The available address pool for a currently active scope is nearly depleted and more computers need to be added to the physical network segment.
• Clients need to be migrated to a new scope.
• Support is needed for DHCP clients on the other side of BOOTP relay agents, where the network on the other side of the relay agent has multiple logical subnets on one physical network. For more information, see “Supporting BOOTP Clients” later in this chapter.
• A standard network with one DHCP server on a single physical subnet is limited to leasing addresses to clients on the physical subnet.

What is Stub zone DNS?
A stub zone is a copy of a zone that contains only those resource records necessary to identify the authoritative Domain Name System (DNS) servers for that zone. A stub zone is used to resolve names between separate DNS namespaces. This type of resolution may be necessary when a corporate merger requires that the DNS servers for two separate DNS namespaces resolve names for clients in both namespaces.
A stub zone consists of:

• 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.

The master servers for a stub zone are one or more DNS servers authoritative for the child zone, usually the DNS server hosting the primary zone for the delegated domain name
What is Active Directory? Active Directory is a network-based object store and service that locates and manages resources, and makes these resources available to authorized users and groups. An underlying principle of the Active Directory is that everything is considered an object—people, servers, workstations, printers, documents, and devices. Each object has certain attributes and its own security access control list (ACL).
What’s the difference between forward lookup zone and reverse lookup zone in DNS?
Forward lookup is name-to-IP address; the reverse lookup is IP address-to-name.
How to transfer roles in Active Directory?
Using Ntdsutil.exe we can transfer roles in Active Directory. To know more regarding role transfer click this link.
How to backup Active Directory and which main file you take in backing of Active Directory?
We can take backup with Ntbackup utility.
Active Directory is backed up as part of system state, a collection of system components that depend on each other. You must backup and restore system state components together.
Components that comprise the system state on a domain controller include:

• System Start-up Files (boot files). These are the files required for Windows 2000 Server to start.
• System registry.
• Class registration database of Component Services. The Component Object Model (COM) is a binary standard for writing component software in a distributed systems environment.
• SYSVOL. The system volume provides a default Active Directory location for files that must be shared for common access throughout a domain. The SYSVOL folder on a domain controller contains:
  • NETLOGON shared folders. These usually host user logon scripts and Group Policy objects (GPOs) for non-Windows 2000based network clients.
  • User logon scripts for Windows 2000 Professionalbased clients and clients that are running Windows 95, Windows 98, or Windows NT 4.0.
  • Windows 2000 GPOs.
  • File system junctions.
  • File Replication service (FRS) staging directories and files that are required to be available and synchronized between domain controllers.
• Active Directory. Active Directory includes:
  • Ntds.dit: The Active Directory database.
  • Edb.chk: The checkpoint file.
  • Edb*.log: The transaction logs, each 10 megabytes (MB) in size.
  • Res1.log and Res2.log: Reserved transaction logs.

Check my previous articles regarding system administrator questionnaire

(Windows Server 2008) System Administrator Interview Question and Answer – Part 2

What is Active Directory Domain Services 2008?

Active Directory Domain Services (AD DS), formerly known as Active Directory Directory Services, is the central location for configuration information, authentication requests, and information about all of the objects that are stored within your forest. Using Active Directory, you can efficiently manage users, computers, groups, printers, applications, and other directory-enabled objects from one secure, centralized location.

What is the SYSVOL folder?

The Sysvol folder on a Windows domain controller is used to replicate file-based data among domain controllers. Because junctions are used within the Sysvol folder structure, Windows NT file system (NTFS) version 5.0 is required on domain controllers throughout a Windows distributed file system (DFS) forest.

This is a quote from microsoft themselves, basically the domain controller info stored in files like your group policy stuff is replicated through this folder structure

What’s New in Windows Server 2008 Active Directory Domain Services?

Active Directory Domain Services in Windows Server 2008 provides a number of enhancements over previous versions, including these:

Auditing—AD DS auditing has been enhanced significantly in Windows Server 2008. The enhancements provide more granular auditing capabilities through four new auditing categories: Directory Services Access, Directory Services Changes, Directory Services Replication, and Detailed Directory Services Replication. Additionally, auditing now provides the capability to log old and new values of an attribute when a successful change is made to that attribute.

Fine-Grained Password Policies—AD DS in Windows Server 2008 now provides the capability to create different password and account lockout policies for different sets of users in a domain. User and group password and account lockout policies are defined and applied via a Password Setting Object (PSO). A PSO has attributes for all the settings that can be defined in the Default Domain Policy, except Kerberos settings. PSOs can be applied to both users and groups.

Read-Only Domain Controllers—AD DS in Windows Server 2008 introduces a new type of domain controller called a read-only domain controller (RODC). RODCs contain a read-only copy of the AD DS database. RODCs are covered in more detail in Chapter 6, “Manage Sites and Replication.”

Restartable Active Directory Domain Services—AD DS in Windows Server 2008 can now be stopped and restarted through MMC snap-ins and the command line. The restartable AD DS service reduces the time required to perform certain maintenance and restore operations. Additionally, other services running on the server remain available to satisfy client requests while AD DS is stopped.

AD DS Database Mounting Tool—AD DS in Windows Server 2008 comes with a AD DS database mounting tool, which provides a means to compare data as it exists in snapshots or backups taken at different times. The AD DS database mounting eliminates the need to restore multiple backups to compare the AD data that they contain and provides the capability to examine any change made to data stored in AD DS.

What is the Global Catalog?

A global catalog server is a domain controller. It is a master searchable database that contains information about every object in every domain in a forest. The global catalog contains a complete replica of all objects in Active Directory for its host domain, and contains a partial replica of all objects in Active Directory for every other domain in the forest.

It has two important functions:

Provides group membership information during logon and authentication

Helps users locate resources in Active Directory

What are RODCs? And what are the major benefits of using RODCs?

A read-only domain controller (RODC) is a new type of domain controller in the Windows Server® 2008 operating system. With an RODC, organizations can easily deploy a domain controller in locations where physical security cannot be guaranteed. An RODC hosts read-only partitions of the Active Directory® Domain Services (AD DS) database.

Before the release of Windows Server 2008, if users had to authenticate with a domain controller over a wide area network (WAN), there was no real alternative. In many cases, this was not an efficient solution. Branch offices often cannot provide the adequate physical security that is required for a writable domain controller. Furthermore, branch offices often have poor network bandwidth when they are connected to a hub site. This can increase the amount of time that is required to log on. It can also hamper access to network resources.

Beginning with Windows Server 2008, an organization can deploy an RODC to address these problems. As a result, users in this situation can receive the following benefits:

* Improved security

* Faster logon times

* More efficient access to resources on the network

What does an RODC do?

Inadequate physical security is the most common reason to consider deploying an RODC. An RODC provides a way to deploy a domain controller more securely in locations that require fast and reliable authentication services but cannot ensure physical security for a writable domain controller.

However, your organization may also choose to deploy an RODC for special administrative requirements. For example, a line-of-business (LOB) application may run successfully only if it is installed on a domain controller. Or, the domain controller might be the only server in the branch office, and it may have to host server applications.

In such cases, the LOB application owner must often log on to the domain controller interactively or use Terminal Services to configure and manage the application. This situation creates a security risk that may be unacceptable on a writable domain controller.

An RODC provides a more secure mechanism for deploying a domain controller in this scenario. You can grant a nonadministrative domain user the right to log on to an RODC while minimizing the security risk to the Active Directory forest.

You might also deploy an RODC in other scenarios where local storage of all domain user passwords is a primary threat, for example, in an extranet or application-facing role.

What is REPADMIN?

Repadmin.exe: Replication Diagnostics Tool

This command-line tool assists administrators in diagnosing replication problems between Windows domain controllers.

Administrators can use Repadmin to view the replication topology (sometimes referred to as RepsFrom and RepsTo) as seen from the perspective of each domain controller. In addition, Repadmin can be used to manually create the replication topology (although in normal practice this should not be necessary), to force replication events between domain controllers, and to view both the replication metadata and up-to-dateness vectors.

Repadmin.exe can also be used for monitoring the relative health of an Active Directory forest. The operations replsummary, showrepl, showrepl /csv, and showvector /latency can be used to check for replication problems.

What is NETDOM?

NETDOM is a command-line tool that allows management of Windows domains and trust relationships. It is used for batch management of trusts, joining computers to domains, verifying trusts, and secure channels

windows server 2008 interview questions and answers

What are some of the new tools and features provided by Windows Server 2008?

Windows Server 2008 now provides a desktop environment similar to Microsoft Windows Vista and includes tools also found in Vista, such as the new backup snap-in and the BitLocker drive encryption feature. Windows Server 2008 also provides the new IIS7 web server and the Windows Deployment Service.

What are the different editions of Windows Server 2008?

The entry-level version of Windows Server 2008 is the Standard Edition. The Enterprise Edition provides a platform for large enterprisewide networks. The Datacenter Edition provides support for unlimited Hyper-V virtualization and advanced clustering services. The Web Edition is a scaled-down version of Windows Server 2008 intended for use as a dedicated web server. The Standard, Enterprise, and Datacenter Editions can be purchased with or without the Hyper-V virtualization technology.

What two hardware considerations should be an important part of the planning process for a Windows Server 2008 deployment?

Any server on which you will install Windows Server 2008 should have at least the minimum hardware requirement for running the network operating system. Server hardware should also be on the Windows Server 2008 Hardware Compatibility List to avoid the possibility of hardware and network operating system incompatibility.

What are the options for installing Windows Server 2008?

You can install Windows Server 2008 on a server not currently configured with NOS, or you can upgrade existing servers running Windows 2000 Server and Windows Server 2003.

How do you configure and manage a Windows Server 2008 core installation?

This stripped-down version of Windows Server 2008 is managed from the command line.

Which Control Panel tool enables you to automate the running of server utilities and other applications?

The Task Scheduler enables you to schedule the launching of tools such as Windows Backup and Disk Defragmenter.

What are some of the items that can be accessed via the System Properties dialog box?

You can access virtual memory settings and the Device Manager via the System Properties dialog box.

When a child domain is created in the domain tree, what type of trust relationship exists between the new child domain and the trees root domain?

Child domains and the root domain of a tree are assigned transitive trusts. This means that the root domain and child domain trust each other and allow resources in any domain in the tree to be accessed by users in any domain in the tree.

What is the primary function of domain controllers?

The primary function of domain controllers is to validate users to the network. However, domain controllers also provide the catalog of Active Directory objects to users on the network.

What are some of the other roles that a server running Windows Server 2008 could fill on the network?

A server running Windows Server 2008 can be configured as a domain controller, a file server, a print server, a web server, or an application server. Windows servers can also have roles and features that provide services such as DNS, DHCP, and Routing and Remote Access.

Which Windows Server 2008 tools make it easy to manage and configure a servers roles and features?

The Server Manager window enables you to view the roles and features installed on a server and also to quickly access the tools used to manage these various roles and features. The Server Manager can be used to add and remove roles and features as needed.

What Windows Server 2008 service is used to install client operating systems over the network?

Windows Deployment Services (WDS) enables you to install client and server operating systems over the network to any computer with a PXE-enabled network interface.

What domain services are necessary for you to deploy the Windows Deployment Services on your network?

Windows Deployment Services requires that a DHCP server and a DNS server be installed in the domain

How is WDS configured and managed on a server running Windows Server 2008?

The Windows Deployment Services snap-in enables you to configure the WDS server and add boot and install images to the server.

What is the difference between a basic and dynamic drive in the Windows Server 2008 environment?

A basic disk embraces the MS-DOS disk structure; a basic disk can be divided into partitions (simple volumes).
Dynamic disks consist of a single partition that can be divided into any number of volumes. Dynamic disks also support Windows Server 2008 RAID implementations.

What is RAID in Windows Server 2008?

RAID, or Redundant Array of Independent Disks, is a strategy for building fault tolerance into your file servers. RAID enables you to combine one or more volumes on separate drives so that they are accessed by a single drive letter. Windows Server 2008 enables you to configure RAID 0 (a striped set), RAID 1 (a mirror set), and RAID 5 (disk striping with parity).

What conceptual model helps provide an understanding of how network protocol stacks such as TCP/IP work?

The OSI model, consisting of the application, presentation, session, transport, network, data link, and physical layers, helps describe how data is sent and received on the network by protocol stacks.

What protocol stack is installed by default when you install Windows Server 2008 on a network server?

TCP/IP (v4 and v6) is the default protocol for Windows Server 2008. It is required for Active Directory implementations and provides for connectivity on heterogeneous networks.

How is a server running Windows Server 2008 configured as a domain controller, such as the domain controller for the root domain or a child domain?

Installing the Active Directory on a server running Windows Server 2008 provides you with the option of creating a root domain for a domain tree or of creating child domains in an existing tree. Installing Active Directory on the server makes the server a domain controller.

What are some of the tools used to manage Active Directory objects in a Windows Server 2008 domain?

When the Active Directory is installed on a server (making it a domain controller), a set of Active Directory snap-ins is provided. The Active Directory Users and Computers snap-in is used to manage Active Directory objects such as user accounts, computers, and groups. The Active Directory Domains and Trusts snap-in enables you to manage the trusts that are defined between domains. The Active Directory Sites and Services snap-in provides for the management of domain sites and subnets.

How are domain user accounts created and managed?

The Active Directory Users and Computers snap-in provides the tools necessary for creating user accounts and managing account properties. Properties for user accounts include settings related to logon hours, the computers to which a user can log on, and the settings related to the user’s password.

What type of Active Directory objects can be contained in a group?

A group can contain users, computers, contacts, and other nested groups.

What type of group is not available in a domain that is running at the mixed-mode functional level?

Universal groups are not available in a mixed-mode domain. The functional level must be raised to Windows 2003 or Windows 2008 to make these groups available.

What types of Active Directory objects can be contained in an Organizational Unit?

Organizational Units can hold users, groups, computers, contacts, and other OUs. The Organizational Unit provides you with a container directly below the domain level that enables you to refine the logical hierarchy of how your users and other resources are arranged in the Active Directory.

What are Active Directory sites in Windows Server 2008?

Active Directory sites are physical locations on the network’s physical topology. Each regional domain that you create is assigned to a site. Sites typically represent one or more IP subnets that are connected by IP routers. Because sites are separated from each other by a router, the domain controllers on each site periodically replicate the Active Directory to update the Global Catalog on each site segment.

Can servers running Windows Server 2008 provide services to clients when they are not part of a domain?

Servers running Windows Server 2008 can be configured to participate in a workgroup. The server can provide some services to the workgroup peers but does not provide the security and management tools provided to domain controllers.

What does the use of Group Policy provide you as a network administrator?

Group Policy provides a method of controlling user and computer configuration settings for Active Directory containers such as sites, domains, and OUs. GPOs are linked to a particular container, and then individual policies and administrative templates are enabled to control the environment for the users or computers within that particular container.

What tools are involved in managing and deploying Group Policy?

GPOs and their settings, links, and other information such as permissions can be viewed in the Group Policy Management snap-in.

How do you deal with Group Policy inheritance issues?

GPOs are inherited down through the Active Directory tree by default. You can block the inheritance of settings from upline GPOs (for a particular container such as an OU or a local computer) by selecting Block Inheritance for that particular object. If you want to enforce a higher-level GPO so that it overrides directly linked GPOs, you can use the Enforce command on the inherited (or upline) GPO.

How can you make sure that network clients have the most recent Windows updates installed and have other important security features such as the Windows Firewall enabled before they can gain full network access?

You can configure a Network Policy Server (a service available in the Network Policy and Access Services role). The Network Policy Server can be configured to compare desktop client settings with health validators to determine the level of network access afforded to the client.

What is the purpose of deploying local DNS servers?

A domain DNS server provides for the local mapping of fully qualified domain names to IP addresses. Because the DNS is a distributed database, the local DNS servers can provide record information to remote DNS servers to help resolve remote requests related to fully qualified domain names on your network.

In terms of DNS, what is a caching-only server?

A caching-only DNS server supplies information related to queries based on the data it contains in its DNS cache. Caching-only servers are often used as DNS forwarders. Because they are not configured with any zones, they do not generate network traffic related to zone transfers.

How the range of IP addresses is defined for a Windows Server 2008 DHCP server?

The IP addresses supplied by the DHCP server are held in a scope. A scope that contains more than one subnet of IP addresses is called a superscope. IP addresses in a scope that you do not want to lease can be included in an exclusion range.

How to configure linux sendmail server step by step guide Example and Implementation

How to configure linux sendmail server step by step 

In a company environment, email is an essential component to the work day. Email is used to communicate with both internal employees and external customers. In exam you will be tested to configure the send mail server for you local LAN.

By default sendmail server allows to connect to local host only. So we should edit the /etc/mail/sendmail.mc file to allow connect to other hosts.

The sendmail daemon is configured from a directory of files in /etc/mail and a directory of configuration files in/usr/share/sendmail-cf. There are two basic configuration files:

• sendmail.cf The main sendmail configuration file.
• sendmail.mc A macro that's easier to edit, which can be used to generate a new sendmail.cf file.

For this example we are using two systems one linux server one linux clients. These are the pre quest for a sendmailserver

• A linux server with ip address 192.168.0.254 and hostname Server
• A linux client with ip address 192.168.0.1 and hostname Client1
• A Configured DNS server on Linux server
• Updated /etc/hosts file on both linux system
• Running portmap and xinetd services
• Firewall should be off on server

We have configured all these steps in our pervious article.

How to configure DNS server step by step guide

We suggest you to review that article and configure DNS server before start configuration of sendmail server. Once you have completed the necessary steps follow this guide.

Configure sendmail server

sendmail and m4 rpm are required to configure sendmail server check them for install if not found install them.


Mail server program reads the /etc/mail/sendmail.cf. To change the configuration on mail server, we should edit the/etc/mail/sendmail.mc file. When Sendmail is started or restarted with the service sendmail restart command a new sendmail.cf file is automatically generated if sendmail.mc has been modified. In exam you should generate it with m4 command.

open /etc/mail/sendmail.mc for editing

show hidden line with : set nu option on vi command mode

By default, the following line limits sendmail access to connect local host only [line no 116] 

You can allow other computers to use your sendmail server by commenting out this line.

In the sendmail.mc file , lines that begin with dnl, which stands for delete to new line, are considered comments. Some lines end with dnl, but lines ending in dnl are not comments

comment this line with dnl keyword followed by # sign

save this file with :wq and exit.

Now generate new sendmail.cf file by using m4 command as shown here


Now restart sendmail service and also set it on with chkconfig

if sendmail service restart without any error means you have configured sendmailsuccessfully.

Configure sendmail client side

We are using another linux system to test sendmail server. All configuration are same as you have done on server system.

Check sendmail and m4 rpm for install. Open /etc/mail/sendmail.mc file and locate line no 116 and put a dnlwith # sing and save file. All step are same which you have done on server.

Now generate new sendmail.cf file by using m4 command as shown here


Now restart sendmail service and also set it on with chkconfig


Testing of sendmail server

We will test sendmail server by sending and receiving mail in lab environment. for this we use two user one on each system.

Now create one user on each system vinita on server

and nikita on client system


Now send mail from user vinita to nikita and from nikita to user vinita and also check each others mail by mail command


Use full user name to send mail. For example to send mail to nikita use nikita@client1 and tosend mail to vinita use vinita@server.example.com