Network Admin Interview Question and Answers

Q:What is Networking?
Inter connection between the two or more computers is called the networking. Using three types of network are Intranet, Internet and Extranet (Eg. LAN, WAN & MAN)

Q:What is Bandwidth?
Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range is called the bandwidth. Every line has a capacity of transmission of data, The maximum amount of data that can be transferred in a single line is called Bandwidth.

Q:What is VLAN?
VLAN Stand for Virtual Local Area Network. It is a logical grouping of network users and resources connected to administratively defined ports on a switch.
Uses of VLAN are as follows:-

1. It is securied connection.
2. It increases flexibility.
3. It creates separate broadcast domain.

Q:What is CIDR?
CIDR Stands for classless inter domain routing. It helps in preventing the wasting of IP address and nowadays we are facing the shortage of the IP address.So this CIDR helps to prevent the waste of IP address.Shortly IPV6 will come into exist.

Q:What is VLSM?
VLSM stands for Variable length subnet mask, when try to separate a major subnet into minor ones, then that process is called VLSM. We can subnet in various lengths.
Eg: can be separated into and

Q:What is unicast?
Unicast is one type of transmission in which information is sent from one host to another host (i.e Source to Destination). In another words, Unicast transmission is between one-to-one nodes

Unicast ---> A transmission to a single interface card.

Q:What is Multicast?

Multicast is such differ from Unicast. It is another type of transmission or communication in which there may be more than host and the information sent is meant for a set of host.(i.e one source to group of destination

Multicast ---> A transmission to a group of interface cards on the network.

Q:What is Broadcast?

Broadcast is one type of transmission in which information is transfer from just one host but is received by all the host connected to the network. (i.e one source to all destination)

Broadcast ---> A transmission to all interface cards on the network.

Q:What is ACL?
ACL stands of Access Control List, It is packet filtering method, which filter the IP packets based on source and destination address. It is set of rules or condition that permit or deny the ip packets.

Cisco ACLs are divided into types.
1. Standard ACL &
2. Extended ACL.

Standard ACL - Standard IP Access Lists ranging in number from 1 to 99. Standard ACL control the traffic based on the source IP address only.

Extended ACL - Extended IP Access Lists ranging in number from 100 to 199. Extended ACL control the traffic based on the source IP address, destination IP address, source port number and destination port number.

Q:What is CEF?
Cisco Express Forwarding (CEF) is an advanced layer 3 switching technology used mainly in large core networks or the Internet to enhance the overall network performance.

CEF is mainly used to increase packet switching speed by reducing the overhead and delays introduced by other routing techniques. CEF consists of two key components: The Forwarding Information Base (FIB) and adjacencies. The FIB is similar to the routing table generated by multiple routing protocols, maintaining only the next-hop address for a particular IP-route.

The adjacency maintains layer 2 or switching information linked to a particular FIB entry, avoiding the need for an ARP request for each table lookup. There are five types of adjacencies:

1. Null adjacency.
2. Punt adjacency.
3. Glean adjacency.
4. Discard adjacency.
5. Drop adjacency.

Q:What is CDP?
CDP Stand for Cisco Discovery Protocol, It's a Layer 2 protocol and used to check the availability of neighbouring Cisco devices. It can give you all the details of the neighbours. CDP provides network device inventory, connectivity information, and IP next hop information. CDP Version-2 (CDPv2) is the most recent release of the protocol and provides more intelligent device tracking features.

Sending CDP packets every 60 seconds and

Hold time is 180 seconds.

Q:What is SNMP?
The Simple Network Management Protocol (SNMP) is an application layer protocol (Layer 1) that facilitates the exchange of management information between network devices. It is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. SNMP enables network administrators to manage network performance, find and solve network problems, and plan for network growth.

Q:What is RIP and difference between Rip V1 & Rip V2?
RIP Stands for Routing information protocol. It is also called distance vector routing protocol. It is open standard for any vendor use. It uses metric as hop count (max hop count 15) AD 120. It sends periodic update for every 30 sec. It is used for small network.

Rip V1
1. It is a Class full Protocol.
2.Classful Protocol: - Supports networks with same Subnet Mask
3.RIPV1 uses Broadcast Address
4.RIPV1 Universal Broadcast (
5. RIPV1 does not VLSM.
Rip V2
1. It is a Classless Protocol.
2.Classless Protocol: - Supports subnetted networks; It carries the information of   subnet mask
3.RIP V2 uses Multicast Address
4. RIPV2 uses Multicast (
5.RIPV2 supports VLSM

Q:What is EIGRP?
EIGRP stands for Enhanced Interior Gateway Routing Protocol, it is also called balanced hybrid routing protocol or advanced distance vector routing protocol. Hello packets for every 5 sec, hold time 15 sec. It support for VLSM, the multicast address is It maintain neighbour table, topology table & routing table
  1. Neighbour – directly connected neighbour (feasible successor)
  2. Topology – all path reach to destination (feasible successor)
  3. Routing – best path (successor)
DUAL Diffusion update algorithm
  1. Successor is available in routing table
  2. If successor failed means it will take the feasible successor
DUAL Parameter
  1. A.D = Advertised distance (Reported Distance)
  2. F.D = Feasible distance
Reported Distance: The metric for a route advertised by a neighbour
Feasible distance: The distance advertised by a neighbour plus the cost to get to that neighbor

Q:What is OSPF?
Open Shortest Path First (OSPF) is a dynamic routing protocol for use in Internet Protocol (IP) networks. OSPF is designated by the Internet Engineering Task Force (IETF). Specifically, it is a link-state routing protocol and falls into the group of interior gateway protocols, operating within an autonomous system (AS). Unlimited router can be used. CPU usage will be high, to reduce the CPU Usage using area.

Q:What are the areas in OSPF?
• The backbone area, which is also referred to as Area 0. All other areas must connect to the backbone area. Hence, this area is obligatory.

• An ordinary or standard area, which is an area that connects to the backbone (Area 0) and is treated as a separate entity. All routers in a standard area have the same topological database, but their routing tables will be based on the routers position in the standard area and will thus be unique to the router.

• A stub area, which is an area that does not accept external summary routes. A router within a stub area can only see outside the autonomous system if a default route has been configuration for it.

• A totally stubby area, which is similar to a stub area. In this area, the default route must be configured as This type of area is useful for remote sites that have few networks and limited connectivity with the rest of the network and is a Cisco proprietary solution.
• A not so stubby area (NSSA), which is a stub area that can receive external routes but will not propagate those external routes into the backbone area.

Q:What are the network types in OSPF?
1. Non broadcast - This is the default on frame relay networks has a DR/BDR election.  Neighbor command needed to establish adjacency.

2. Broadcast - This is the default on Ethernet/broadcast networks.  Does have DR/BDR election.

3. Point-to-point -  No DR/BDR election.  This one is pretty self explanatory.

4. Point-to-multipoint - Does not have a DR/BDR election. Solves some design issues with the next hop processing for NONBROADCAST.  Treats as a collection of P2P links.

5. Point-to-multipoint non broadcast - Same as P2M but does not use pseudo broadcast.  Must statically define neighbors.

6. Loopback - OSPF treats these as stub hosts. (/32)

Q:What are BGP and their attributes?
The Border Gateway Protocol (BGP) is an inter autonomous system routing protocol. An autonomous system is a network or group of networks under a common administration and with common routing policies. BGP is used to exchange routing information for the Internet and is the protocol used between Internet service providers (ISP). Customer networks, such as universities and corporations, usually employ an Interior Gateway Protocol (IGP) such as RIP or OSPF for the exchange of routing information within their networks. Customers connect to ISPs, and ISPs use BGP to exchange customer and ISP routes. When BGP is used between autonomous systems (AS), the protocol is referred to as External BGP (EBGP). If a service provider is using BGP to exchange routes within an AS, then the protocol is referred to as Interior BGP (IBGP).
BGP Attributes  are
1. Weight                                              5. AS_path
2. Local preference                                 6. Next hop
3. Multi-exit discriminator                         7. Community

Q:What is PPPoE?
Point to Point Protocol over Ethernet (PPPoE) is network protocols that allow data communication between two network entities or points, which supports network layer protocols including IPv4 and IPv6. PPP supports three types of user authentication protocols that provide varying levels of security.
  1. PAP                          2.  CHAP                                3.  EAP
1. Clear text
1. Encrypted
2. Less secure
2. High secure
3. Two way handshake method
3. Three way handshake method
         Auth. Request
         Auth. Acknowledgment

4. No periodic Check up
4. Periodical Check up
Extensible Authentication Protocol (EAP) is most commonly used for authentication on wireless networks

Q:What are the timers for dynamic routing protocol?

60 sec
10 sec
Update timers
30 sec
90 sec

Dead timers
180 sec

Q:What is the AD Value for Dynamic routing protocols?


Active Directory Domain Services Command Reference

Active Directory Domain Services (AD DS) command-line tools are built into Windows Server 2008. They are available if you have the AD DS or Active Directory Lightweight Directory Services (AD LDS) server role installed. To use these tools, you must run them from an elevated command prompt. To open an elevated command prompt, click Start, right-click Command Prompt, and then click Run as administrator

Extends the Active Directory schema and updates permissions as necessary to prepare a forest and domain for a domain controller that runs the Windows Server 2008 operating system.
Imports and exports data from Active Directory using files that store data in the comma-separated value (CSV) format. You can also support batch operations based on the CSV file format standard.

Analyzes the state of domain controllers in a forest or enterprise and reports any problems to help in troubleshooting.

Installs and removes Active Directory Domain Services (AD DS).

Displays and changes permissions (access control entries) in the access control list (ACL) of objects in AD DS.

Adds specific types of objects to the directory.

Exposes Active Directory data that is stored in a snapshot or backup as a Lightweight Directory Access Protocol (LDAP) server.

Provides database utilities for Active Directory Lightweight Directory Services (AD LDS).

Displays the selected properties of a specific object in the directory.

Provides management facilities for Active Directory Lightweight Directory Services (AD LDS).

Modifies an existing object of a specific type in the directory.

Moves a single object in a domain from its current location in the directory to a new location or renames a single object without moving it in the directory tree.

Queries AD DS according to specified criteria.

Deletes an object of a specific type or any general object from the directory.

Creates, modifies, and deletes directory objects on computers running Windows Server 2003 or Windows XP Professional operating systems.

Makes it possible for users to perform operations against an LDAP-compatible directory, such as AD DS. These operations include connect, bind, search, modify, add, and delete.

Makes it possible for administrators to manage Windows Server 2003 and Windows 2000 domains and trust relationships from a command prompt.

Net computer
Adds or deletes a computer from a domain database.

Net group
Adds, displays, or modifies global groups in domains.

Net user
Adds or modifies user accounts, or displays user account information.

Performs network administrative tasks.

Provides management facilities for AD DS.

Redirects the default container for newly created computers to a specified target organizational unit (OU) so that newly created computer objects are created in the specific target OU instead of in CN=Computers.

Redirects the default container for newly created users to a specified target OU so that newly created user objects are created in the specific target OU instead of in CN=Users.

Makes it possible for administrators to diagnose Active Directory replication problems between domain controllers running Windows operating systems.

Makes it possible for administrators to read, modify, and delete the Service Principal Names (SPN) directory property for an Active Directory service account.

New features in AD DS in Windows Server 2008

New features in AD DS in Windows Server 2008

In Windows Server 2008, organizations can use Active Directory Domain Services (AD DS) to manage users and resources, such as computers, printers, or applications, on a network. AD DS includes many new features that are not available in previous versions of Windows Server Active Directory. These new features make it possible for organizations to deploy AD DS more simply and securely and to administer it more efficiently. This topic provides an overview of the improvements in AD DS. For details about the improvements, see the following topics that describe the new features in Windows Server 2008 AD DS:

AD DS: Auditing.

AD DS: Fine-Grained Password Policies.

AD DS: Read-Only Domain Controllers.

AD DS: Restartable Active Directory Domain Services.

AD DS: Database Mounting Tool (Snapshot Viewer or Snapshot Browser).

AD DS: User Interface Improvements.

AD DS: Owner Rights. 
AD DS: Auditing
The global audit policy Audit directory service access controls whether auditing for directory service events is enabled or disabled. This security setting determines whether events are logged in the Security log when certain operations are carried out on objects in the directory. You can control what operations to audit by modifying the system access control list (SACL) on an object. In Windows Server 2008, this global audit policy is not enabled by default. Although the subcategory Directory Service Access is enabled for success events by default, the other subcategories are not enabled by default.

If you define this policy setting (by modifying the default Domain Controllers Policy), you can specify whether to audit successes, audit failures, or not audit at all. Success audits generate an audit entry when a user successfully accesses an AD DS object that has a SACL specified. Failure audits generate an audit entry when a user unsuccessfully attempts to access an AD DS object that has a SACL specified.

You can set a SACL on an AD DS object on the Security tab in that object's properties dialog box. Audit directory service access is applied in the same manner as Audit object access; however, it applies only to AD DS objects and not to file system objects and registry objects.

AD DS: Fine-Grained Password Policies
You can use fine-grained password policies to specify multiple password policies within a single domain. You can use fine-grained password policies to apply different restrictions for password and account lockout policies to different sets of users in a domain.

For example, you can apply stricter settings to privileged accounts and less strict settings to the accounts of other users. In other cases, you might want to apply a special password policy for accounts whose passwords are synchronized with other data sources.

AD DS: Read-Only Domain Controllers
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.

AD DS: Restartable Active Directory Domain Services
Restartable AD DS reduces the time that is required to perform certain operations. AD DS can be stopped so that updates can be applied to a domain controller. Also, administrators can stop AD DS to perform tasks, such as offline defragmentation of the Active Directory database, without restarting the domain controller. Other services that are running on the server and that do not depend on AD DS to function, such as Dynamic Host Configuration Protocol (DHCP), remain available to satisfy client requests while AD DS is stopped.

AD DS: Database Mounting Tool
Although the Active Directory database mounting tool does not recover deleted objects by itself, it helps streamline the process for recovering objects that have been accidentally deleted. Before the Windows Server® 2008 operating system, when objects or organizational units (OUs) were accidentally deleted, the only way to determine exactly which objects were deleted was to restore data from backups. This approach had two drawbacks:
  • Active Directory had to be restarted in Directory Services Restore Mode to perform an authoritative restore. 
  • An administrator could not compare data in backups that were taken at different points in time (unless the backups were restored to various domain controllers, a process which is not feasible). 
The purpose of the Active Directory database mounting tool is to expose AD DS data that is stored in snapshots or backups online. Administrators can then compare data in snapshots or backups that are taken at different points in time, which in turn helps them to make better decisions about which data to restore, without incurring service downtime.

AD DS: User Interface Improvements
AD DS user interface (UI) improvements provide new installation options for domain controllers. Furthermore, the updated Active Directory Domain Services Installation Wizard streamlines and simplifies AD DS installation.

AD DS UI improvements also provide new management options for AD DS features such as read-only domain controllers (RODCs). Additional changes to the management tools improve the ability to find domain controllers throughout the enterprise. They also provide important controls for new features such as the Password Replication Policy for RODCs.

AD DS: Owner Rights
Owner Rights is a well-known security principal that you can add to the DACL of an object to specify the permissions that are assigned to owners of objects in the directory service. This added security feature overrides the default behavior of owners of objects in the system. Because owners of objects (as specified in the security descriptor of the object) have WRITE_DAC permission, they can give rights to themselves and to other security principals as they see fit.

The Owner Rights security principal is specified using the well-known security identifier (SID) S-1-3-4. For example, if the Owner Rights security principal is located in the domain, its distinguished name (also known as DN) can be expressed this way: CN=Owner Rights,CN=WellKnown Security Principals,CN=Configuration,DC=fabrikam,DC=com.

By default, Owner Rights are not defined on objects. This means that the pre–Windows Server 2008 behavior of owners having WRITE_DAC permissions to the objects that they own still applies.

When you add the Owner Rights security principal to objects, you can specify what permissions are given to the owner of an object. For example you can specify in the access control entry (ACE) of an object that the owner of a particular object is given Read permissions or you can specify NULL permissions to an object, which grants the owner of the object no permissions.