Basic CCNA Networking Interview Questions & Answers

Basic CCNA Networking Interview Questions & Answers

Basic CCNA Networking Interview Questions & Answers
  • Define Network?

Network in general terms means a group of devices, connected with the help of some media in order to share some resources from a source to a destination and networking is a process of sharing the resources.

  • What is a Link?

Link is a physical or a logical component of a network to interconnect nodes or devices.

  • What is a node?

Node is a connection point on network for data transmission. It can be a computer or printer or any type of device that is capable of sending and receiving the data over the network.

  • What is a gateway?

Gateway is a node of a network which can be used as an entrance for other network. It is a piece of hardware and different from default gateway.

  • What is point-point link?

A connection between two nodes of the network is referred as point to point network and that link which connects both nodes is point to point link.

  • What is Multiple Access?

Multiple Access allows more than one devices to transmit data at the same time span. Star or Mesh topology can be used for this.

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  • What’s the benefit of subnetting?

With the help of subnetting we can break a large network into smaller networks and assign IP addresses to those networks without changing our major network. It helps in utilizing our IP addresses more efficiently.

  • What is BGP (Border Gateway Protocol)?

BGP is an exterior gateway protocol used to connect two or more different autonomous systems. It is widely being used to route the traffic of Internet. It can also work for internal AS but we have better protocols for internal connectivity. It has Administrative distance of 20 for external routes and 200 for internal routes.

  • What is Gateway-to-Gateway protocol?

Gateway-to-Gateway protocol is now obsolete. This was being used for routing datagrams between internet gateways. It uses Minimum hop Algorithm.

  • What is a Multi-homed Host?

Multi-homed host is defined as a node connected with more than one networks. Like a PC can be connected with both Home network and a VPN. These kind of hosts can be assigned with multiple addresses, one for each network. 

  • What is OSPF?

OSPF stands for Open Shortest Path First. It is a link state routing protocol that can connect a large number of networks without having any limitation to number of hops. It uses Dijkstra Algorithm and considers Cost as its’ metric. It has AD of 110 and uses the concepts of Areas, Router-id, Process-id and Virtual link for connectivity.

  • What is Routing?

Routing is a process of exchanging route information form one router to another. Without routing it is impossible to connect two or more networks located at different or same geographical areas.

  • What is a Protocol?

Protocol is set of rules on which a sender and a receiver agrees to transmit the data. Protocols are responsible for data communication in between networks.

  • Explain difference between Router,Switch and Hub ?

Following are the differences in Hub, Routers and Switches,


Hubs operate at Layer 1 of OSI model.

Hubs cannot process layer-2 or layer-3 traffic. Layer-2 deals with hardware addresses and layer-3 deals with logical (IP) addresses. So, hubs cannot process information based on MAC or IP addresses.

Hubs cannot even process data based on whether it is a unicast, broadcast or multi-cast data.

Hub transfers data to every port excluding the port from where data was generated.

Hubs work only in half duplex mode.

Collisions can happen.

In case of a collision, a hub rejects data from all the devices and signals them to send data again. Usually devices follow a random timer after which data is sent again to hub.

Maximum 2-12 number of ports can be found on Hubs.


Switches are network devices that operate on layer-2 of OSI model. Some switches operate at higher level too.

Switches are also known as intelligent hubs.

Switches operate on hardware addresses (MAC) to transfer data across devices connected to them.

It performs broadcast at first, after that Unicast.

Major difference between Bridge and Switch being that a switch forwards data at wire speed as it uses special hardware circuits known as ASICs.

Switches support full duplex data transfer communication.

As layer 2 protocols headers have no information about network of data packet so switches cannot forward data based or networks and that is the reason switches cannot be used with large networks that are divided in sub networks.

Switches can avoid loops through the use of spanning tree protocol.

Switches can have 24-48 ports and can be practically unlimited ports because they don’t divide speed unlike Hubs.


Routers are the network devices that operate at Layer-3 of OSI model.

As layer-3 protocols have access to logical address (IP addresses) so routers have the capability to forward data across networks.

Routers are far more feature rich as compared to switches.

Routers maintain routing table for data forwarding.

Routers have lesser port densities as compared to switches.

Routers are usually used as a forwarding network elements in Wide Area Networks. 

  • What is Checksum?

A checksum is a count of the number of bits in a transmission data that is included with the data so that the receiver can check to see whether the same number of bits arrived. If the counts match, it’s assumed that the complete transmission was received.

  •  What is Redundancy ?

Redundancy is a method of insuring network availability in case of network or path failure. Generally referred as backup paths in a networks.

  • What are the criteria necessary for an effective and efficient network?

For an effective network, there must be alternate paths available, convergence should be fast and whatever happens network should never go down. Network should be cost effective and properly secure.

  • What is the key advantage of using switches?

Switch doesn’t broadcast on all the ports. They can be managed and vlans cab be created. They are fast, can store MAC addresses. They also don’t divide the speed on each ports.

  • When does network congestion occur?

Congestion can occur cause of the over capacity of the media. When a media carries data beyond its limit, congestion can happen.

  • Does a bridge divide a network into smaller segments? 

NO, bridge doesn’t divide a network in smaller segments.

  • What is the difference between OSI and TCP/IP Model ?

Following are the differences in TCP/IP and OSI Model.

OSI(Open System Interconnection) TCP/IP (Transmission Control Protocol / Internet Protocol)
OSI is a generic, protocol independent standard, acting as a communication gateway between the network and end user. 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.
OSI model has a separate Presentation layer and Session layer. TCP/IP does not have a separate Presentation layer or Session layer.
OSI is a reference model around which the networks are built. Generally it is used as a guidance tool. TCP/IP model is, in a way implementation of the OSI model.
Network layer of OSI model provides both connection oriented and connectionless service. The Network layer in TCP/IP model provides connectionless service.
Protocols are hidden in OSI model and are easily replaced as the technology changes. In TCP/IP replacing protocol is not easy.
OSI model defines services, interfaces and protocols very clearly and makes clear distinction between them. It is protocol independent. In TCP/IP, services, interfaces and protocols are not clearly separated. It is also protocol dependent.
It has 7 layers It has 4 layers
  • What is the size of IP Address?

IPv4 is a 32 bits address and IPv6 is 128 bits address.

  • What is the range of class C address?

Class C varies from 192 – 223.

  • What is PoE (Power over Ethernet) ?

PoE allows electrical current to be carried by the cable rather than the power cords. It minimizes the number of wires required to install the network.

  • What are the advantages of Distributed Processing?

Lower cost, reliability, improved performance, reduced processing time, flexibility are the advantages of Distributed processing. 

  • When were OSI model developed and why its standard called 802.XX and so on?

In Feb 1980, OSI model was developed. In 802.xx, 80 represent 1980 and 2 represents February.

  • What is Full form of AD?

Administrative Distance 

  • What is a peer-peer process?

The processes on each machine that communicate at a given layer are called peer to peer process.

  • What is the difference between broadcast domain and collision domain ?

Broadcast domain is a domain where if a broadcast frame is forwarded, every devices pays attention and receives the data. While in Collision domain,chances of data collision is maximum. Like in Hub , if two or more send traffic at the same time, data will collide in between and none of the devices will receive the data.

  • What is ping? Why you use ping?

Ping is a utility used to test the connectivity in the network. It stands for Packet Internet Groper.

  • Explain difference between straight and crossover cable with examples ?

Straight cable is used to connect two different layer devices like router-switch, router-pc, and switch-pc while cross cable is used to connect two same layer devices like router-router, switch-switch, and pc-pc. Color coding for both cable is different. If color coding on both ends of the cable is same, it is a straight cable, while if 1<–>3, 2<–>6 is being used, it is a cross cable for data transfer.

  • What is the difference between tracert and traceroute

Tarcert works on PC while Traceroute works on routers.

  • What is Round Trip Time?

RTT is the propagation time between two nodes. It is the time taken to send a packet out of the interface and receiving the acknowledgement.

  • Define the terms Unicasting, Multiccasting and Broadcasting and Anycasting?

Unicasting means “one on one” communication, Multicasting means “one to many” communication but there must be atleast one devices that is not receiving the traffic while broadcasting means “one to all” communication. Each device receives packets in case of broadcasting. Anycast works in IPv6 and it means to “one to nearest” communication.

  • How many pins do serial ports of routers have?

In computer it’s known as com port and could be available in 9pin or 25 pin. On router it have 60 pins. 

  • What are the differences between static ip addressing and dynamic ip addressing?

In static IP Addressing, IP addresses are assigned by Network Administrator while in Dynamic, IP addresses are assigned with the help of a DHCP server.

  • Difference between CSMA/CD and CSMA/CA ?

CSMA/CD is responsible for detecting collision in wired media mainly, while CSMA/CA works on wireless media to completely avoid collision because detecting collision in wireless media is a bit hard.

  • What is DHCP scope?

DHCP Scope is the range of IP Addresses from which DHCP server will be assigning IP Addresses to the clients.

  • What are the different memories used in a CISCO router?

Flash, RAM, NVRAM and ROM are the memories available in the router.

  • What are the different types of passwords used in securing a CISCO router?

Enable password, Secret Password, Line passwords (VTY, Console and Aux) are the passwords used in Router.

  • What is the use of “Service Password Encryption” ?

Service Password Encryption command encrypts plain text password into type 7 password. These are not very much secure and can be easily decrypted.


  • Briefly explain the conversion steps in data encapsulation.?

Process of adding header and trailer information in data is called Data Encapsulation. Whenever a layer passes the data to next layer it adds some extra information in data. This is called header. Next layer then processes the data and adds its own header. This process continues until data is place on physical media. This process is called Encapsulation. Removing header and trailer information from the data is called Data Decapsulation.

  • In configuring a router, what command must be used if you want to delete the configuration data that is stored in the NVRAM?

Erase startup-config is the command to delete preconfigured files on the router.

  • IEEE standard for wireless networking?


  • What is the range of class A address?

From 0 – 127, but we cannot use 0 and 127, so actual range is from 1 to 127

  • What is the range of class B address?

From 128 – 191.

  • Differentiate Logical Topology from Physical Topology?

Physical topology represents the physical structure i.e cabling of the network while logical topology deals with the data flow in the network.

  • what is AS (Autonomous System) ?

A group of devices under a single administration is called an AS.

  • What is the difference between Private IP and Public IP ?

Public IP addresses are for global routing over internet. They are allocated to the websites and companies to access the internet. They are unique worldwide if connected to Internet. Private IP addresses are for local use and are not routable over internet. They can be same in different organization.

  • Explain different cable types ?

Straight, Cross, Serial, Console are some cable types used in networking. Serial cable is used to connect a router to another router. Console cable is used to access the router or switches from a PC.

  •  How does RIP differ from EIGRP?

Following are the differences in RIP and EIGRP,

AD value: That is administrative distance which determines the trust worthiness of the routing protocol. For Rip it is 120, EIGRP it is 90 internal / 170 external.

RIP uses Bellmen ford algorithm to calculate the path while EIGRP use Dual method to calculate the routes paths

Maximum hop count for RIP is 15 that is after 15 counts the packet is dropped while that of EIGRP is 100 by default and up to 255 by configuration. By default 100.

There is difference between their refresh timers.

EIGRP uses an Autonomous number to determine which domain it belongs to which is not the case with RIP protocols.

RIP is mostly used for smaller networks which EIGRP is used for larger networks.

RIP is a distance vector routing protocol while EIGRP is a Link state routing protocol.

RIP is classful protocol whereas EIGRP is classless protocol

In RIP full routing table exchanged, but in EIGRP missing routes are exchanged

For RIP protocol, update timer is 30 seconds but in EIGRP hello timer every 5 seconds

  • Differentiate User Mode from Privileged Mode

Commands applied on user mode cannot effect the router while some commands of privilege mode can change the configurations. In user mode, no configuration can be made. We can only check the reachability and some basic commands in that mode. While in Privilege mode we can save, delete and modify the configuration files.

  • What is 100BaseFX?

100BASE-FX is a version of Fast Ethernet over optical fiber.

  • Differentiate full-duplex from half-duplex ?

In full duplex, user can send and receive data at the same time while in half duplex user can either receive or send the data at a time.

  • What does the show protocol display?

The show protocols command shows the global and interface-specific status of any configured Level 3 protocol.