Networking interview questions with answers

 How to troubleshoot network connectivity?

–Network cable connections

Make sure that the cables that connect the computer to the Internet or your home network are secured firmly. Additionally, make sure that the network devices that your computer uses are turned on and working correctly. Then, follow these steps to verify network connectivity, as appropriate for your situation.

• For wireless network users, ensure that the computer is within the acceptable range from the wireless router or access point and Wireless switch is turned “ON”

Make sure that network adapter is working fine by going into Device Manager. (Start>Run>type devmgmt.msc)

–Network adapter in a computer

 * Check for devices that have down arrow or yellow exclamation points overlaid on their icons.

* If problems are noted in the Device Manager, the component most likely has any of the following problems:

–Has a device driver issue, is disabled, or is malfunctioning.

– Check Network configuration on a computer

* Navigate to Control Panel > Troubleshooting, Select Network and Internet > Select Network Adapters to initiate the Diagnosis.

–However, Windows 7 provides the option to troubleshoot using the Network Diagnose function.

–Right click on the Network Device > Diagnose > Verifying that any required servers are online.

Check with Networking Commands

Windows 7 provides a number of TCP/IP tools for troubleshooting network connectivity problems

–IPCONFIG -

This command displays TCP/IP configuration settings for the local computer.

•IPCONFIG is executed from a command prompt and is available in Windows NT, Windows 2000, Windows XP and Windows 7.

•This utility is essential for troubleshooting networking issues and determining valid IP addresses for the local machine and the IP address for the router port of the LAN .

Steps for using IPCONFIG: –

* Open the command prompt window by navigating to: Start > Run

* Type CMD and click OK

* In the Command Prompt, type: IPCONFIG or IPCONFIG /all

Ipconfig : displays the IP address, subnet mask, and default gateway

IPCONFIG /all displays the information from IPCONFIG along with the MAC address, DHCP server, DNS server, and WINS servers

It also displays the full TCP/IP configuration for all adapters.

* Without this parameter, ipconfig displays only the IP address, subnet mask, and default gateway values for each adapter

•Adapters represent physical interfaces, such as installed network adapters, or logical interfaces, such as dial-up connections .

IPCONFIG /? used for viewing additional options.

However, we have more commands for troubleshooting

Ipconfig /release: Releases (Deletes) DHCP-supplied configuration information.

•Sends a DHCPRELEASE message to the DHCP server to:

–Release the current DHCP configuration

–Discard the IP address configuration for all adapters (if an adapter is not specified)

–Discard the IP address for a specific adapter if the adapter parameter is included

TCP/IP Troubleshooting Tools

Ipconfig /renew: Renews (Assigns new Ip address) DHCP-supplied configuration information

*Renews DHCP configuration for all adapters (if an adapter is not specified) or for a specific adapter if the Adapter parameter is included.

*This parameter is available only on computers with adapters that are configured to obtain an IP address automatically.

*To specify an adapter name, type the adapter name that appears while using ipconfig without parameters.

Ipconfig /flushdns: Purges (Deletes all the old cookie files of tcp/ip which was used earlier for communication) the local DNS cache (the area of memory that stores recently resolved names so that the client does not have to contact the DNS server each time the client needs to resolve a name)

•Flushes and resets the contents of the DNS client Resolver cache

•During DNS troubleshooting, this procedure is used to discard negative cache entries from the cache, as well as any other entries that have been added dynamically .

Ipconfig /registerdns: Renews (Freshly configure new details from DHCP server)DHCP-supplied configuration information and registers the DNS name to IP address information with DNS

 *Initiates manual dynamic registration for the DNS names and IP addresses that are configured at a computer.

•This parameter is used to troubleshoot a failed DNS name registration or resolve a dynamic update problem between a client and the DNS server without rebooting the client computer.

•The DNS settings in the advanced properties of the TCP/IP protocol determine the names registered in DNS.

Ipconfig /displaydns: Displays the contents of the local DNS cache.

•Displays the contents of the DNS Client Resolver cache.

–The DNS Client Resolver includes entries preloaded from the local Hosts file and any recently obtained resource records for name queries resolved by the computer

•The DNS Client service uses this information to resolve frequently queried names quickly, before querying its configured DNS servers.

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–Ping : This command verifies connections between the host computer and the pinged computer,

*This is done by sending Internet Control Message Protocol (ICMP) echoes

*Four echoes are sent to a target host, and four response echoes are then received from the target host

Using PING command you can ping an IP address, a NetBIOS name (if a WINS server is available), or a Fully Qualified Domain Name (FQDN) (if a DNS server is available).

You can test adapter by typing loopback address:

Ex :  ping 127.0.0.0 or Ping loopback.

If you want to reset the TCP/IP settings follow the steps given below:

·  At the command prompt, enter the following command, and then press Enter:

netsh int ip reset c:\resetlog.txt

Note If you don't want to specify a directory path for the log file, run the following command instead:

netsh int ip reset resetlog.txt

·  Restart the computer.

You can also try pinging neighbors Ip address for testing connectivity.

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–Net view :  used to test TCP/IP connections,

•To use Net View:

–Log on with the proper credentials that are required to view shares on a remote or local computer

–Open a command prompt

–Type net view \\ComputerName or net view \\IP Address

–The result lists the file and print shares on the computer

–If there are no file or print shares on the computer, the message There Are No Entries In The List is displayed

•If the Net View command fails, check the following:

–Check the computer name by going in the System Properties dialog box

–Check the gateway or router address in the TCP/IP Properties dialog box

–Check the gateway or router status

The remote computer is running the File And Printer Sharing for Microsoft Networks Service (this service can be added in the TCP/IP Properties dialog box)

–Tracert : This command is used to sends ICMP (Internet Control Message Protocol) echoes to each hop to the destination and reports information and errors

–A hop is usually a router port

•This utility can identify where wide area network connectivity is affected

•The Tracert command executes from the command prompt

–Tracert the FQDN (Fully qualified domain name) or IP address.

•Steps:

–Type tracert at the command prompt followed by the IP address or FQDN of the remote computer.

–The resulting report shows where the packets were lost

•This information can be used to uncover the source of the problem.

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–Pathping :  It’s a combination of both Ping and Tracert, displaying information about packet loss at every router between the host computer and the remote one.

•The Pathping command provides information about data loss between the source and the destination, allowing the user to determine which particular router or subnet might be having network problems.

•Type pathping at the command prompt followed by the target name or IP address.

 

 What is the difference between a switch and a router?

Switch : It's an Intelligent networking device used for connecting devices into same network.

Router : It is Device which is used to connect two different networks into one network to share resources with each other.

Computers can be connected to each other via a switch or a router. So what is the difference between the two? The most basic explanation is that a switch is designed to connect computers within a network, while a router is designed to connect multiple networks together.
In a home network, a single router is usually all that is required for connecting devices to the Internet. All devices within a home, such as computers, tablets, and smart phones can connect to the router via a wired or wireless connection. As the name implies, the router routes all connected devices to a cable or DSL modem.
Switches are most often used in large networks, such as those found in business and school environments. They connect many computers together within a single local area network, or LAN. A large network may include multiple switches, which connect different groups of computer systems together. These switches are typically connected to a router that allows connected devices to access the Internet.
Even though routers and switches are different, they can be used interchangeably. For example, a router typically has several LAN ports and a single WAN port. The LAN ports are designed for connecting computers via Ethernet. The WAN port is designed to connect to the modem. While switches do not a have WAN port, you can use any of the standard LAN ports to connect to a modem. However, you may have to use a crossover Ethernet cable in order for the connection to work properly.
Though it may be possible to use a switch as a router, switches typically do not have the same configuration options as routers do. Switches used to be faster than routers, but modern routers are capable of the same performance. Therefore, when choosing a central device for your home network, a router makes the most sense.

What is the difference between a router and a modem?

Answer: Routers and modems are two of the most common computer peripherals, yet many people don't know the function of each one. While the two devices may look similar, they each serve a difference purpose. Fortunately, the functions of the two devices are pretty easy to understand.
A router is a small box that allows multiple computers to join the same network (see below).

While early routers provided several Ethernet ports for wired connections, most modern routers offer wireless connectivity as well. These "wireless routers" often have one or two moveable antennas on the sides, though some models house the antennas inside the enclosure. Wireless routers allow multiple computers and other devices, such as smart phones and tablets, to join the same network.

While connecting to a router provides access to a local network (LAN), it does not necessarily provide access to the Internet. In order for devices on the network to connect to the Internet, the router must be connected to a modem. Therefore, most routers have a specific Ethernet port that is designed to connect to the Ethernet port of a cable or DSL modem.
A modem is a device that provides access to the Internet (see below).

The modem connects to your ISP, which typically provides either cable or DSL Internet service. Cable modems have a coaxial (or "coax") connection, which is the same type of connector found on a TV or cable box. This connects to a cable port on the wall. DSL modems have a telephone connector, also called an RJ-11 jack, which connects to a telephone socket on the wall.
By connecting your modem to your router (instead of directly to a computer), all devices connected to the router can access the modem, and therefore, the Internet. The router provides a local IP address to each connected device, but they will all have the same external IP address, which is assigned by your ISP.
To summarize, the device connection order is outlined below:

1. PC or wireless device
2. Router
3. Modem
4. ISP
5. Internet

While the router and modem are usually separate entities, in some cases, the modem and router may be combined into a single device. This type of hybrid device is sometimes offered by ISPs to simplify the setup process.

Which is faster -- Kbps or Mbps?

Answer: Kbps stands for "kilobits per second," while Mbps stands for "megabits per second." Because one megabit is equal to 1024 kilobits, 1.0 Mbps is over 1000 times faster than 1.0 Kbps.
Note that the lowercase "b" in Kbps and Mbps means "bit," not byte. One byte is equal to eight bits. For example, 2 MBps equals 16 Mbps. This is a small but important difference to be aware of. Data transfer rates are typically measured in bits, while data storage capacity is usually measured in bytes.

What does a server do?

Answer: A server is a computer that serves information to other computers. These computers, called clients, can connect to a server through either a local area network (LAN) or a wide area network (WAN), such as the Internet.

There are a number of different types of servers, including Web servers, mail servers, and file servers. A web server serves Web pages to computers that connect to it. It also can parse scripting languages such as PHP, ASP, and JSP. A mail server stores users' e-mail accounts and sends and receives e-mail messages. For example, when you send an e-mail to a friend, the message is sent by a mail server, using the SMTP protocol. A file server is a computer that stores files that can be accessed by other computers. File servers are often used within local networks and typically require a password or some kind of authentication to connect to it.

These are a few examples of some common servers, but several other types of servers exist. Just about any computer can be used as a server if the necessary server software is installed on it. While servers typically don't need a lot of processing power, lots of RAM and fast hard drives are helpful for dealing with heavy traffic to and from the server.