Likely CCNA Interview Questions and Answers.

As a network engineer, when searching for your dream job, your employee might hit with the following questions below to test your IT knowledge. The questions might be little tricky but if you listen attentively you may hear some things like these once I listed here.

You might be ask to….

Define PAP and CHAP.


PAP- Password Authentication Protocol

CHAP- Challenge Handshake Authentication Protocol

PAP sends username and password checks and validates users.

CHAP- challenge message passes and replies with username and password so no other router can come inside.

How many collision domains and broadcast domains are available in router, switch and hub?


Router- Each port has one separate collision domain and one separate broadcast domain.

Switch- Each port has one separate collision domain but all ports have one single broadcast domain.

Hub- All ports have one collision domain and one broadcast domain.

Which router command is used to display RAM contents?


Show run/show running-config

Which router command is used to display NVRAM (Non-volatile random-access memory) contents?


Show start/show start-config.

What does the command “show version” do?


It displays iOS version, RAM space availability, process speed.

What is the subnet mask of the following IP addresses-, and 200.2..2.2?


What is broadcasting and which addresses are used for broadcasting?


Broadcasting means passing data to all devices in the n/w. In a n/w if there are 5 systems, and we send data to all 5 systems; it is broadcasting.

Both receiving and sending by all devices.

Broadcasting IP address: or

Broadcasting MAC address: ffff:ffff:ffff or ff:ff:ff:ff:ff:ff

What is multicasting and which addresses are used for multicasting?


In a Network if there are 10 Machines and if we send datas to more than one machine but not all 10 Machines it is called Multicasting.For example sending datas to some 5 machines instead of all 10 Machines.Class D IP address is used for Multicasting ranging from from 224.x.x.x to 239.x.x.x and the MAC address starting from 0100:5EXX:XXXX series where 0100:5E is the Organizationally Unique Identifier Address.

Which IP addresses can be given as private addresses?


Class a- to

Class b- to

Class c- to

40) What is APIPA?


APIPA is Automatic Private IP Addressing.
Ranges= to (class b)
Autoconfiguration enabled, this means APIPA is set in the system.
It is used to automatically assign private IP addresses for home/small business n/ws that contains a single subnet, has no DHCP server and is not using static IP address.

What is NTP and what is its purpose?


NTP- Network Time Protocol
It is an open standard that allows you to synchronize your router’s time with a centralized time server. It is implemented mostly while using Syslog on the networks. Its port no is 123, it uses the UDP (User Datagram Protocol).

What is SNMP and what are its main functions?


SNMP is used for network traffic management- port no: 161.

SNMP contains three elements-

Network management application (SNMP manager)

SNMP agents (running inside a managed device)

MIB (Management Information Base), database object that describes the information in a predetermined format; that the agent can use to populate the data.

On what algorithm does OSPF work?


OSPF works on Dijkstra Algorithm.

First a shortest path tree is constructed.

Secondly Routing table is populated with the resulting best paths.

What are the major functions of SNMPv3?




Message integrity

It uses HMAC-SHA for security.

What is EIGRP?


EIGRP- Enhanced Interior Gateway Routing Protocol
It is a balanced hybrid protocol, a Cisco proprietary protocol.
The symbol of EIGRP is D.
DUAL (Diffusing Update Algorithm). If primary route fails, EIGRP can use backup or feasible routes.

What is OSPF?


OSPF (Open Shortest Path First). It is an open standard routing protocol that has been implemented by a wide range of network vendors, including Cisco. It supports multi vendors like Cisco, Alcatel, Juniper, 3Com routers. Administrative distance of OSPF is 110, symbol is O.

In what ways can we choose DR in OSPF?


Highest priority

Highest router ID

Highest IP address

What do you mean by BPDU Guard in switch?


BPDU Guard is used to protect the integrity of switch ports that have portfast enabled. By default, BPDU guard is disabled; it is mainly used to shut the port in an error condition.

What are the major states in switch?







What are the two protocols used in EtherChannel?


EtherChannels can be negotiated between two switches to provide some dynamic link configuration. Two protocols are available to negotiate bundled links in catalyst switches- PAgP (Port Aggregation Protocol), LACP (Link Aggregation Control Protocol).

PAgP can be used only in Cisco devices but LACP can be used in other vendors also.

What are the modes of LACP?


There are two modes of LACP: a) passive mode, and b) active mode.

What are the modes of PAGP?


There are two modes of PAGP, namely- Auto and Desirable.

What are the seven layers available in OSI model?


Layer 7- Application Layer

Layer 6- Presentation Layer

Layer 5- Session Layer

Layer 4- Transport Layer

Layer 3- Network Layer

Layer 2- Data Link Layer

Layer 1- Physical Layer

What is HSRP?


Hot Standby Router Protocol (HSRP). HSRP is a redundancy protocol developed by Cisco to provide gateway redundancy without any additional configuration on the end devices in the subnet.

User Datagram Protocol (UDP) port 1985 is used by HSRP active and standby routers to send Hello messages. These hello messages are forwarded to multicast address to communicate between routers in the HSRP group.

This aim of the above blog post is to help you get equipped for the task ahead of you in the IT industry.

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