Ccna 60 Interview Questions&answers

LATEST 60 CCNA INTERVIEW QUESTIONS WITH ANSWERS

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1) What are the two types of IP addresses available? There are two types, namely IPv4 and IPv6 IPv4- 32 bit address and IPv6-128 bit address.

2) Which IP address is used for loopback address and for what purpose? 127.0.0.1 is used for loopback address and also for local testing purposes. Loopback means looping to our own systems, checking our own systems. It is used to test whether TCP/IP stack is correctly installed.

3) What do you mean by OSI layers? Open System Interconnection (OSI) layers. 

It is a set of rules used to describe how to make networks.

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Whenever we design new network or hardware device, we have to follow OSI reference model.

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There are seven layers, which means seven set of rules; they are designed by ISO (international standard organization).

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It tells what are the services/ports/applications used.

4) What are the major functions of transport layer? 

Segment fragmentation

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Numbering segmenting

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Reliable and unreliable data delivery

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Error detection & error correction

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Flow control

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Multi tasking

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Windowing

5) What is data encapsulation and data de-encapsulation? 

When data is sent from a higher layer to a lower layer, each layer adds some information to the original data; this is called as encapsulation. The information added is called as header.

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When data is sent from lower layer to higher layer, each layer will remove information from the other layer. This is called as de-encapsulation.

6) What are the major functions of routers? a) Packet switching- all incoming data is switched to packets. It deals only with packets (data with IP address) b) Packet filtering- router sends and receives only packets. It is used in WAN, so all incoming packets are filtered mainly for security. c) Internetwork communication- joining of two or more networks. d) Path selection- router is used to select the shortest and best path from source to destination. e) QoS- Quality of Service: QoS is the ability of the n/w to provide better or special service to a set of users or applications.

7) What is the main purpose of DHCP? 

DHCP is dynamic host configuration protocol.

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DHCP allows devices to acquire their addressing information dynamically.

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DHCP is actually based on bootstrap protocol (bootp).

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It is built on a client/server model and defines two components.

1. Server- delivering host configuration information 2. Client- requesting and acquiring host configuration information

8) What are the two types of cables available? 

Straight through cable

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Crossover cable

9) Which registry key is used in normal mode of router and what registry key is used to recover password? 

The registry key used in normal mode is 0x2102 to 0x210f.

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To recover password we have to use the registry key 0x2142.

10) Define CDP and its functions? 

CDP is Cisco discovery protocol

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It is a layer 2 protocol

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It works based on mac addresses.(h/w addresses)

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It is used to find adjacent Cisco devices.

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It is a Cisco proprietary protocol means used to find only the neighbouring Cisco devices.

It is used to find out 1. IP addresses 2. Port numbers 3. iOS details 4. Router models 5. Switch models 6. Interface details 7. Device ID- hostname

11) What are the two types of routes available in routers?

A) Static or Static default Static, if one route is fixed for transmission it will stay fixed. If that link is down it cannot connect and reach the destination even if there are alternate paths. Static route is used for smaller networks. Symbol of static is “s”. Static default– it sends data to unknown destination + specified n/w.ex in isp we can have different connections. It uses 0.0.0.0 as the address for connection. Symbol of static default is “s*”. B) Dynamic route It will choose the path by itself. Paths are found by the routing protocols. Chooses the best or main path. If that path fails, it will find out the next alternate path. Routing protocols like RIP/EIGRP/OSPF decide the paths.

12) What is distance vector? Explain with example. Distance Vector Protocols send periodic updates every 30 secs or at some time interval to the adjacent routers. In case if there is a link failure immediately they inform to update only after 30 secs. For example, RIP routing information protocol is a distance vector protocol. Here distance indicates length between two routers and vector means in which link direction the link is connected between them.

13) What is the administrative distance of RIP, EIGRP and OSPF? The administrative distance for: 

RIP: 120.

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EIGRP: 90

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OSPF: 110

14) What is switching? Switching is the process of using the hardware address/mac address of devices on a LAN to segment a n/w. Switches break up large collision domains into smaller ones and that a collision domain is a n/w segment with two or more devices sharing the same bandwidth. Switch is a layer device and deals with frames (data with mac address).

15) What is meant by VLAN and what is its purpose? A VLAN is a logical and orderly alignment of network users and resources. These are connected to ports on a switch which are administratively defined. It is used to segment big networks and connect with routers for security purposes. For joining two different networks or virtual VLANs, we need routers.

16) What happens if there is no VLAN in switch ports? If there is no VLAN in switches, it can lead to a broadcast storm; as all ports will start broadcasting. By default all ports in switches are in VLAN1 and they can send and receive data within VLAN1. We can also create multiple VLANs and join them using routers.

17) What are the two ports of switches? 1. Access port 2. Trunk port 

An Access port belongs to and carries the traffic of only one VLAN. We can pass only single VLAN information. It is used to connect switch ports with computers with minimum speed of 10Mbps.

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A Trunk port is used for multiple connections between switch to routers and switch to switch.

Switch to router- minimum speed: 100mbps. It is used for inter VLAN communications, when connected with the router.

18) What is VTP? VTP is VLAN trunking protocol. It is used to allow VLAN information to be automatically propagated throughout the switching environment.

19) What are the various of modes in VTP?

There are three modes in VTP: 

Server mode

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Client mode

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Transparent mode

Default mode is server. 

Server mode- Full control over VLAN creations and modifications for their domains.

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Client mode- VTP clients do not allow the administrator to create, change or delete any VLAN’s; instead they listen to the VTP’s advertisements from other switches and modify their VLAN configuration accordingly.

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Transparent mode- VTP transparent mode switches will not participate in VTP advertisements. It can create and delete VLAN’s that are local only to itself. It will not propagate to other switches, and will not advertise its own VLAN configuration.

20) Define STP. Why is it used? STP (Spanning Tree Protocol) was created by digital equipment corporation. The new version was created by IEEE which is 802.1d. STP is a bridge-to-bridge protocol used to maintain a loop free n/w. Redundant links between switches are a good idea because they help prevent complete network failures in the event one link stops working.

21) How many bits are available in IPv6? 

IPv6 contains 128 bits with 8 groups. It has n/w part and host part. Each group has 16 bits.

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So 8*16=128, it is in hexadecimal format (00ff). There are 32 hexadecimal numbers.

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Each groups(4 hex digits) are separated by colon.

22) What are the multicast addresses used in IPv4 and IPv6 by different protocols?

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OSPF (IPv4)=224.0.0.5,224.0.0.6

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OSPF(IPv6)=ff02::5/ff02::6

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RIP (IPv4)=224.0.0.9

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RIPng(IPv6)=ff02::9

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EIGRP(IPv4)=224.0.0.10

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EIGRP(IPv6)=ff02::10

23) What is EUI in IPv6? EUI is Extended Unique Identifier 64. It is an interface ID, which is typically composed of mac addresses. We can create a EUI-64 interface in a 48 bit mac address by inserting the “0xfffe” between the upper three bytes and lower three bytes of the mac address.

24) What do you mean by global unicast address in IPv6? 

Global unicast addresses are IPv6 public addresses, which can be used globally as public addresses and are unique in nature; e.g. 2000::1, 3001::1

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Any address which begins with hex 2 or 3.

25) What are the major differences between IPv4 and IPv6 addressing? IPv4 address is 32 bit address and IPv6 is 128 bit address. In IPv4 only 232 addresses are available which is 4.3 billion addresses out of which only 3.7 billion are actually usable (many are reserved like class d,e and private). In IPv6 many millions of addresses are there, it has 3.4*1038 addresses.

26) What is ACL and what are the major types available? ACL (Access Control List) is a list of commands/statements used in routers to filter packets. There are three types of ACL: 1. Standard 2. Extended 3. Named

27) What is WAN and what is the main purpose? 

WAN (Wide Area Network); used to connect between two cities.

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WANs connect remote sites over large geographic area.

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Connection requirements vary depending on user requirements, cost, and availability.

28) What are the major protocols used in WAN? 

Point-to-Point Protocol (PPP)

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Serial Line Internet Protocol (SLIP)

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High-level Data Link Control Protocol (HDLC)- The default protocol.

29) What is frame relay? Frame relay is a packet switching technology; it is used to join two or more routers with a single interface. It is cheaper in cost and belongs to ISP.

30) What is LMI? LMI (Local Management Interface) is a signaling standard that is used between the routers and frame relay switches. It allows for passing information about the operation and status of the virtual circuit between the provider’s n/w and the DTE (Data Circuit-terminating equipment).

31) Define PAP and CHAP. 

PAP- Password Authentication Protocol

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CHAP- Challenge Handshake Authentication Protocol

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PAP sends username and password checks and validates users.

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

32) 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.

33) Which router command is used to display RAM contents? Show run/show running-config

34) Which router command is used to display NVRAM (Non-volatile random-access memory) contents? Show start/show start-config.

35) What does the command "show version" do? It displays iOS version, RAM space availability, and process speed.

36) What is the subnet mask of the following IP addresses- 10.0.0.1, 160.1.1.1 and 200.2.2.2? 

10.0.0.1- 255.0.0.0

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160.1.1.1- 255.255.0.0

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200.2.2.2- 255.255.255.0

37) What is broadcasting and which addresses are used for broadcasting?

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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.

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Both receiving and sending by all devices.

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Broadcasting IP address: 255.255.255.255 or 255.255.255.255/32

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

38) 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 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.

39) Which IP addresses can be given as private addresses? 

Class a- 10.0.0.0 to 10.255.255.255

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Class b- 172.16.0.0 to 172.31.255.255

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Class c- 192.168.0.0 to 192.168.255.255

40) What is APIPA? APIPA is Automatic Private IP Addressing. Ranges= 169.254.0.1 to 169.255.255.254 (class b) Auto configuration 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.

41) What is Syslog and why is it used? Syslog server is a popular server used to store log information- port no: 514. It can be configured easily. It can store a large volume of data. By default logging, messages are sent to the router’s console port. It can also be sent to Syslog.

42) 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).

43) What is SNMP and what are its main functions? 

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

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SNMP contains three elements-

1. Network management application (SNMP manager) 2. SNMP agents (running inside a managed device) 3. MIB (Management Information Base), database object that describes the information in a predetermined format; that the agent can use to populate the data.

44) On what algorithm does OSPF work? OSPF works on Dijkstra Algorithm. 

First a shortest path tree is constructed.

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Secondly Routing table is populated with the resulting best paths.

45) What are the major functions of SNMPv3? 1. Authentication 2. Encryption 3. Message integrity 

It uses HMAC-SHA for security.

46) 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.

47) 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.

48) In what ways can we choose DR in OSPF? 1. Highest priority 2. Highest router ID 3. Highest IP address

49) 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.

50) What are the major states in switch? 1. Disabled 2. Blocking 3. Listening 4. Learning 5. Forwarding

51) 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 switchesPAgP (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.

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

53) What are the modes of PAGP? There are two modes of PAGP, namely- Auto and Desirable.

54) What are the seven layers available in OSI model? 

Layer 7- Application Layer

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Layer 6- Presentation Layer

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Layer 5- Session Layer

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Layer 4- Transport Layer

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Layer 3- Network Layer

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Layer 2- Data Link Layer

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Layer 1- Physical Layer

55) 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 224.0.0.2 to communicate between routers in the HSRP group.

56) What is VLSM? VLSM (Variable Length Subnet Mask) is used to apply a different subnet mask to a same class address.

57) What is the subnet mask of 192.168.100.1/28? The subnet mask of 192.168.100.1/28 is 255.255.255.240.

58) Which router command is used to enable IPv6? IPv6 unicast-routing

59) What do you mean by administrative distance? It is used to find which routing protocol is trusted. We can have any number of routing protocols. Each of them can have different paths, values ranging from 0 to 255.

60) What is ISATAP? Intra-site Automatic Tunnel Addressing Protocol (ISATAP). It uses virtual links to connect IPv6 localities together within a site that is primarily using IPv4.