Top 20 questions every Fresher should know
1.Tell me something about yourself?
2.What do you know about our company?
3.What is a router?
Ans: Router is a device which is used to route traffic between the networks. It takes the decision whether to forward or to drop the traffic depending on the destination network.
4.What is meant ARP and RARP?
Ans: ARP is Address Resolution Protocol which is used to map an IP address to a physical machine.
RARP is Reverse Address Resolution Protocol which is used to map MAC address to the IP address.
5.What is IP address ? What is Private IP and Public IP ?
Ans: IP address is a numerical representation to uniquely identify every node (computers, printers, phones, cameras, etc.) in the network. An IP address is not considered to be an IP address unless it is followed by the network mask. It is a 32 bit decimal address separated by dot (e.g. 10.10.10.10/24).
Public IP address is an IP address which is allowed to have the access over the Internet.
Private IP address is the one which is assigned within a company to the users to access the internal resources.
The Internet Assigned Numbers Authority (IANA) reserves the following IP address blocks for use as private IP addresses:
10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.25
6.What is subnetting ?
Ans: Subnetting is partitioning a major network block of IP addresses to assign it to different sites or to use it for different purposes. For example, if a company has been assigned IP address block of 10.0.0.0/8 for their internal use and they have multiple branch offices where they want them to be assigned as per the number of users they can divide this major network block into multiple smaller networks (10.0.0.0/24, 10.0.0.0/25, etc.) and assign it as per the requirement of the sites.
Dividing the network into a number of subnets provides the following benefits:
Reduces the volume of broadcasts
Helps to contain the information to a particular group of people in LAN.
7.What are the different layers of OSI model?
Ans: Basically, there are 7 layers of OSI model. Each layer has its own functionality in the OSI model. They are:
Layer 1 – Physical
Layer 2 – Data Link Layer
Layer 3 – Network
Layer 4 – Transport
Layer 5 – Session
Layer 6 – Presentation
Layer 7- Application
8.What is a Switch and why are we using Switches?
Ans: A switch, in networking can be defined as a device which is used to switch traffic within a given network. Switch takes the decision to forward the traffic based on the media access control (MAC) address of the frames. Whenever a switch receives a frame, it checks the MAC address and decides whether to unicast, broadcast or multicast it. Switch never sends the traffic out the same port it has received it. Reasons why we use switches:
Switches provide a large number of ports to supports users to connect to the network unlike router which has limited number of ports. Basically, it expands your network.
Hub divides the total bandwidth among the users connected to it causing latency and delay in network whereas the switch eliminates this issue and enhances the overall network performance for the users.
9.What is the difference between Switch, Routers, and Hub?
| Routers | Switches | Hubs |
| Used to route traffic between the networks | Used to forward traffic within the network | Used to forward traffic within the network |
| Is a Layer 3 device | Can be used as Layer 2 or Layer 3 device | Is a Layer 2 device |
| Mostly, used as a gateway to any network | Generally used to expand the network | Used as an extension for your network. |
| It takes the forwarding decision based on IP address. | It takes the forwarding decision based on MAC address. | It does not take any forwarding decision and simply broadcasts the frames it receives on any port. |
| Bandwidth is not shared among the users | Bandwidth is shared between the users. |
10.What are the different classes and ranges of IP address?
| Class | 1st Octet Decimal Range | 1st Octet High Order Bits | Network/Host ID (N=Network, H=Host) | Default Subnet Mask | Number of Networks | Hosts per Network (Usable Addresses) |
| A | 1 – 126* | 0 | N.H.H.H | 255.0.0.0 | 126 (27 – 2) | 16,777,214 (224 – 2) |
| B | 128 – 191 | 10 | N.N.H.H | 255.255.0.0 | 16,382 (214 – 2) | 65,534 (216 – 2) |
| C | 192 – 223 | 110 | N.N.N.H | 255.255.255.0 | 2,097,150 (221 – 2) | 254 (28 – 2) |
| D | 224 – 239 | 1110 | Reserved for Multicasting | |||
| E | 240 – 254 | 1111 | Experimental; used for research |
| Class | Address Range |
| Class A | 1.0.0.1 to 126.255.255.254 |
| Class B | 128.1.0.1 to 191.255.255.254 |
| Class C | 192.0.1.1 to 223.255.254.254 |
| Class D | 224.0.0.0 to 239.255.255.255 |
| Class E | 240.0.0.0 to 254.255.255.254 |
11.What is VLAN ? Why it is used ?
A VLAN (Virtual LAN) is a logical grouping of devices. VLAN helps to group certain devices which are geographically separated but are part of same network or are meant to be in one department. For example, an organization can have different VLANs for their internal departments like one for HR, one for Operations, one for their Sales team. Below listed are the advantages of VLAN:
Security – Separating systems that have sensitive data from the rest of the network decreases the chances that people will gain access to information they are not authorized to see.
Broadcasts/Traffic flow – Network traffic is never allowed to leave one VLAN. Thus, containing the broadcast to only particular group of devices and not affecting the whole network.
Flexibity – Logical grouping prevents the users to be bound by geographical conditions.
12.What is the difference between static and dynamic IP addresses?
Ans: As the name suggests, Static IP address is fixed in nature and does not change until it is manually changed by the ISP or network administrator. It is usually assigned to the servers, mail servers etc. The associated risk of website hacking is large in static IP address as it is always constant. Devices assigned static IP are easily trackable.
The dynamic IP address is usually configured on the devices using DHCP protocol, and it frequently changes. Each time the user connects to the network its dynamic IP changes. Dynamic IP uses DHCP and DNS to identify free IP address and to assign it to the user asking for it. Risk associated to the dynamic IP in hacking is less as compared to Static IP addresses. The tracking of the device is difficult as the IP address is always changing.
13.What is OSPF? Describe it.
OSPF stands for Open Shortest Path First. It uses Dijkstra algorithm and is a link state routing protocol which is used to connect to a large number of networks without having any limitation on the number of hops.
14.What is DHCP ?
15.Explain the basic difference between TCP/IP and OSI model.
Differences between TCP/IP and OSI model:
| OSI(Open System Interconnection) | TCP/IP(Transmission Control Protocol / Internet Protocol) |
| 1. OSI is a generic, protocol independent standard, acting as a communication gateway between the network and end user. | 1. TCP/IP model is based on standard protocols around which the Internet has developed. It is a communication protocol, which allows connection of hosts over a network. |
| 2. In OSI model the transport layer guarantees the delivery of packets. | 2. In TCP/IP model the transport layer does not guarantees delivery of packets. Still the TCP/IP model is more reliable. |
| 3. Follows vertical approach. | 3. Follows horizontal approach. |
| 4. OSI model has a separate Presentation layer and Session layer. | 4. TCP/IP does not have a separate Presentation layer or Session layer. |
| 5. Transport Layer is Connection Oriented. | 5. Transport Layer is both Connection Oriented and Connection less. |
| 6. Network Layer is both Connection Oriented and Connection less. | 6. Network Layer is Connection less. |
| 7. OSI is a reference model around which the networks are built. Generally it is used as a guidance tool. | 7. TCP/IP model is, in a way implementation of the OSI model. |
| 8. Network layer of OSI model provides both connection oriented and connectionless service. | 8. The Network layer in TCP/IP model provides connectionless service. |
| 9. OSI model has a problem of fitting the protocols into the model. | 9. TCP/IP model does not fit any protocol |
| 10. Protocols are hidden in OSI model and are easily replaced as the technology changes. | 10. In TCP/IP replacing protocol is not easy. |
| 11. OSI model defines services, interfaces and protocols very clearly and makes clear distinction between them. It is protocol independent. | 11. In TCP/IP, services, interfaces and protocols are not clearly separated. It is also protocol dependent. |
| 12. It has 7 layers | 12. It has 4 layers |
16.What is EIGRP ? Describe it ?
EIGRP is an advanced distance-vector routing protocol. It is a Cisco proprietary routing protocol based on their original IGRP (Interior Routing Protocol). EIGRP uses the Diffusing-Update Algorithm (DUAL) to determine the best route to a destination. Administrative Distance of internal EIGRP routes is 90 and external is 170. Neighborship criteria for any two routers in EIGRP is —
They should belong to same AS.
Their K value should match.
It maintains three different tables:
Neighbor table: having details of all the EIGRP neighbors.
Routing table: having details of the best path to reach any network.
Topology table: having details of all the routes to reach any network.
Some of the features of EIGRP:
EIGRP uses DUAL for rapid convergence. It selects a successor as the best path for a network and at the same time keep feasible successor the second best path for that same network.
It supports VLSM. So it can be easily used with discontiguous network.
It only sends the change in network as updates to its neighbor and not the whole routing table.