Basic CCNA Interview Questions AND Answers

What is Routing?
Routing is the process of selecting best paths in a network and forward data from source to destination through it. Routing is usually performed by a dedicated device called a router.

What is Protocol?
A 'protocol' is a set of invisible computer rules that enable two devices to connect and transmit data to one another. Protocols determine how data are transmitted between computing devices and over networks.

Explain difference between Router, Switch and Hub?
Hubs, switches, and routers are all computer networking devices with varying capabilities. Let's look in detail
A hub is typically the least expensive, least intelligent, and least complicated of the three. Its job is very simple – anything that comes in one port is sent out to the others. Hub has single collision domain and single broadcast domain
Switch is a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model and therefore support any packet protocol. Switches have multiple collision domains and have a single broadcast domain
Router is a device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Routers won't forward broadcast. If a router is present in a network, we may have at least TWO broadcast domains.

Explain broadcast and collision domain?
A broadcast domain is a logical division of a computer network, in which all nodes can reach each other by broadcast at the data link layer.
            A collision domain is a section of a network where data packets can collide with one another when being sent on a shared medium or through repeaters

What is the size of IP Address?
32 bit for IPv4 and 128 bit for IPv6

IEEE standard for wireless networking?
IEEE 802.11

What is the range of class A address?
Class A Range from to and Supports 16 million hosts on each of 127 networks.

What is the range of class B address?
Class B range from to and Supports 65,000 hosts on each of 16,000 networks.

What is the range of class C address?
Class C range is from to and Supports 254 hosts on each of 2 million networks.

What is PoE (Power over Ethernet)?
Power over Ethernet or PoE describes the technology which pass electrical power along with data on Ethernet cabling. This allows a single cable to provide both data connection and electrical power to devices such as wireless access points or IP cameras.

What is a peer-peer process?
A peer-to-peer (P2P) network is a type of decentralized and distributed network architecture in which individual nodes in the network (called "peers") act as both suppliers and consumers of resources. There will be no centralized system we usually seen like Client server model. Simply in p2p, network devices act as both client and server

What is ping? Why you use ping?
Ping [Packet Internet Groper PING] a computer network tool used to test whether a particular host is reachable across an IP network

What is the difference between tracert and traceroute
Both Tracert and traceroute commands do similar purpose. On a router or switch you would use the command traceroute and on a pc you would use tracert .

What is Round Trip Time?
Round-trip time (RTT), also called round-trip delay, is the time required for a packet to travel from a specific source to a specific destination and back again.Source is the computer sending the packet and the destination is a remote computer or system that receives the packet and retransmits it. A user can determine the RTT to and from an IP address by pinging that address

Define the terms Unicast, Multicast and Broadcast and Anycast?
Unicast – One to One communication                    Eg: http
Multicast – One to a group Communication          Eg: SLP
Broadcasting – One to All communication            Eg: ARP
Anycast – One to nearest Communication             Eg : 6to4

Where do we use cross and standard cable?
To connect same group device use Cross Cable
To connect different group device use Straight Cable
For Example:
To connect one PC to another PC use Cross Cable
To connect one comp to switch OR one switch to router use straight cable

What are the differences between static ip addressing and dynamic ip addressing?
Dynamic IP addresses can change each time you connect to the Internet, while static IP addresses are reserved for you statically and don't change over time. In short, Dynamic IP addresses are provided by DHCP server and static IP addresses are given manually

Difference between CSMA/CD and CSMA/CA?
Carrier Sense Multiple Access With Collision Detection (CSMA/CD) is a media access control method used in local area networking using early Ethernet technology to overcome collision when it happened while Carrier sense multiple access with collision avoidance (CSMA/CA) is used in wireless network to avoid collision

What is DHCP scope?
A Dynamic Host Configuration Protocol (DHCP) scope is the consecutive range of possible IP addresses that the DHCP server can lease to clients on a subnet.

What is Checksum?
A simple error-detection scheme in which each transmitted message is accompanied by a numerical value based on the number of set bits in the message. The receiving station then applies the same formula to the message and checks to make sure the accompanying numerical value is the same. If not, the receiver can assume that the message has been garbled.

What is Redundancy?
Network redundancy is a method which provide a back up for the primary device or route and thereby ensuring network will be available even the primary device or route become failed or unavailable

What are the different memories used in a CISCO router?

ROM is read-only memory available on a router's processor board. The initial bootstrap software that runs on a Cisco router is usually stored in ROM. ROM also maintains instructions for Power-on Self Test (POST) diagnostics.

Flash Memory
Flash memory is an Electronically Erasable and Re-Programmable memory chip. The Flash memory contains the full Operating System Image (IOS, Internetwork Operating System).Flash memory retains content when router is powered down or restarted.

RAM is very fast memory that loses its information when the router is shutdown or restarted. On a router, RAM is used to hold running Cisco IOS Operating System, IOS system tables and buffers RAM is also used to store routing tables,RAM Provides temporary memory for the router configuration file of the router while the router is powered on.

RAM Stores running Cisco IOS Operating System, Active program and operating system instructions, the Running Configuration File, ARP (Address Resolution Protocol) cache, routing tables and buffered IP Packets.

NVRAM (Non-volatile Random Access Memory)
NVRAM is used to store the Startup Configuration File. This is the configuration file that IOS reads when the router boots up. It is extremely fast memory and retains its content when the router is restarted.

What are the different types of passwords used in securing a CISCO router?
Here are the five passwords you can set on a Cisco router:
·        Console
·        Aux
·        VTY
·        Enable password
·        Enable Secret

What is the use of "Service Password Encryption"?
"Service Password Encryption" command allows you to encrypt all passwords(including clear text) on your router so they cannot be viewed from your running-config

Define and explain the five conversion steps of data encapsulation.
Data encapsulation is a process that makes use of the layered model concept in that each layer depends on the layer above and below relative to OSI. The lower layer uses encapsulation to put the data from the upper layer into its own encapsulated data field i.e., the information in a protocol is wrapped, or contained, in the data section of another protocol.
In the process of encapsulation, header information is added to the data from the above layer.
The five steps of conversion are
Layers Involved
Step 1
Alphanumeric input from user converted into Data
Step 2
Data converted into segments
Step 3
Segments converted into Packets or Datagrams and Network Header is added
Step 4
Packets or Datagrams are built into Frames
Data Link
Step 5
Frames are converted into bits( 1s and 0s) for transmission

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

      Which command is used to copy the configuration from RAM to NVRAM
      #Copy running-config startup-config

Differentiate Logical Topology from Physical Topology?
Physical topology is the network what we can see and Logical topology is the network which data packets are send from source to destination 

What is AS (Autonomous System)?
An autonomous system (AS) can be said as either a single network or a group of networks that is controlled by a common network administrator (or group of administrators) on behalf of a single administrative entity (such as a university, a business enterprise, or a business division). An autonomous system is also sometimes referred to as a routing domain. An autonomous system is assigned a globally unique number, sometimes called an Autonomous System Number (ASN).

What is the difference between Private IP and Public IP?
Public IP is used across internet and Private IPs are used within the local LAN

Explain different cable types?
Straight cable – To connect different group devices (Switch – Router)
Cross Cable - To connect same group device (PC –PC, SwitchSwitch)
Rollover cable – To connect Console port to Computer

How does RIP differ from EIGRP?
      The major difference between both is that EIGRP is Cisco propriety and RIP is open standard
Some internal differences between them are:
·        AD value of Rip is 120 and AD value for EIGRP 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 upto 255 by configuration.
·        RIP(ver 1) is classfull protocol where as EIGRP is classless protocol
·        In RIP full routing table exchanged, but in EIGRP missing routes are exchanged
·        For RIP protocol, hello timers every 30 seconds but in EIGRP hello timer every 5 seconds
·        RIP v1 sends updates as broadcast while EIGRP send updates as Multicast
·        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 an hybrid routing protocol.
·        RIP sends full update whenever network change occurs whereas EIGRP sends triggered updates

Differentiate User Mode from Privileged Mode
Privileged mode has access to the entire router or switch configuration. User EXEC mode only has limited options. Specifically, to do any configuration changes, you need to enter privileged mode first.User EXEC mode is used mainly for running show commands and to collect details

What is 100BaseFX?
100BaseFX is a version of Fast Ethernet that is often used for wiring campus backbones.

Differentiate full-duplex from half-duplex?
Full-duplex means that communication can occur in both directions at the same time. Half-duplex means communication can only occur in one direction at a time

What does the "show protocol" display?
      To display the configured protocols, use the show protocols command in user EXEC or privileged EXEC mode.
#show protocols [interface-name interface-number]

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  7. Simple notes and easy to understand.. ty mates.

  8. whay is the size of ip address?
    IPV4 -32 bit and IPV6-64 BIT

    1. there is no answer to this type of questions...Ur question like why earth is round?

  9. Tks very much for your post.

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  10. Easily Understood this notes .. please also upload some notes

  11. Tks very much for your post.

    Avoid surprises — interviews need preparation. Some questions come up time and time again — usually about you, your experience and the job itself. We've gathered together the most common questions so you can get your preparation off to a flying start.

    You also find all interview questions at link at the end of this post.

    Source: Top 10 interview questions and answers

    Best rgs

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