Network Interview Questions & Answers

1.      What is the difference between TCP and UDP

TCP is a connection oriented protocol, which means that everytime a packet is sent say from host A to B, we will get an acknowledgement. Whereas UDP on the other hand, is a connection less protocol.

Where will it be used : TCP -> Say you have a file transfer and you need to ensure that the file reaches intact, and time is not a factor, in such a case we can use TCP.

UDP-> Media Streaming, question is say you are watching a movie…would you prefer that your movie comes..perfectly….but u need to wait a long time before you see the next frame ?..or would you prefer the movie to keep streaming…Yes…The second option is definely better….This is when we need UDP

2.      What is a MAC address?

MAC is a machines Physical address, The internet is addressed based on a logical addressing approach. Say, when the packet reaches say the bridge connection a LAN, the question is..how does it identify, which computer it needs to send the packet to. For this it uses the concept of ARP, Address Resolution Protocol, which it uses over time to build up a table mapping from the Logical addresses to the Physical addresses. Each computer is identified using its MAC/Physical address ( u can use the ipconfig -all option to get ur MAC address).

3.      What is MTU?

The MTU is the “Maximum Transmission Unit” used by the TCP protocol. TCP stands for Transmission Control Prototcol. The MTU determines the size of packets used by TCP for each transmission of data. Too large of an MTU size may mean retransmissions if the packet encounters a router along its route that can’t handle that large a packet. Too small of an MTU size means relatively more overhead and more acknowledgements that have to be sent and handled. The MTU is rated in “octets” or groups of 8 bits. The so-called “official” internet standard MTU is 576, but the standard rating for ethernet is an MTU of 1500.

4.      Difference Between. Switch , Hub, Router..

Hub: 1.it is a layer1 device..used to connect various machine on Lan.
2.It forwards broadcast by default.
3.It supports one collision domain and one broadcast domain.
4.it works on Bus topology resulting less speed.
Switch: 1. A layer2 device.
2. Forward broadcast first time only.
3. one broadcast domain & collision domains depends on no. of ports.
4.It is based on Star Topology giving 100mbps to every pc on Lan.
Router: 1. Does not Broadcast by default.
2. breaks up Broadcast domain.
3. Also called Layer3 switch.

5.      VPN.....
VPN(Virtual Private Network )… these are basically the logical networks on the physical line… you can have many VPN over same line..
Need of VPN arises when your company need to increase the network but don’t want to buy any more switches.. take an eg. your dept. your room is packed with employees and ur company need to add 4 more persons to ur deptt. what will they do.. the solution is to create VPN’s…you can configure the switch ports in other deptts. and create a specific VLAN of urdeptt. So that the persons can sit there and access to the required pcs.

6.      ARP & RARP.....

      Stands for Address Resolution Protocol…whenever a request is sent by a node on one network to the node on another network the Physical address(MAC) is required and for this the IP address need to be flow over the network..whenever a router with that network (IP) gets the msg. the required MAC address is sent through the network this process of converting the IP address to MAC address is Called ARP..and the reverse thats the convertion of the Mac address to the IP address is called RARP ( Reverse Address Resolution Protocol)

7.      What is the difference between layer 2 and layer 3 in the OSI model?

Layer 2 is responsible for switching data whereas Layer 3 is responsible for routing the data.

Layer3: With information gathered from user, Internet protocol make one IP packet with source IP and Destination IP and other relevant information. It can then route packet through router to the destination.

Layer2: Soon after it receives IP packet from layer 3, it encapsulate it with frame header (ATM header in case of ATM technology) and send it out for switching. In case of Ethernet it will send data to MAC address there by it can reach to exact destination.