INTERVIEW QUESTIONS

CCNA Level

CCNA Level


Question 1:.What is three types of LAN traffic?
Answer: Unicasts - intended for one host.
Broadcasts - intended for everyone.
Multicasts - intended for an only a subset or group within an entire network.

Question2: What are unicast frames?
Answer: Unicast frames are the most common type of network traffic. A unicast frame is a frame intended for only one host. The only station that processes this frame is one station that has its own MAC address in the destination portion of packet.

Question 3: What is the destination address of broadcast frames?
Answer: The destination address of broadcast frames (Layer 2 broadcast addresses) is FF-FF-FF-FF-FF-FF, or all 1s in binary.

Question 4:  What is Routing?
Answer: Routing is the process of finding a path on which data can pass from source to destination. Routing is done by a device called rout ers, which are network layer devices.

Question 5:  What is the purpose of the Data Link?
Answer:The job of the Data Link layer is to check messages are sent to the right device. Another function of this layer is framing.

Question 6: What are synchronous links?
Answer: Synchronous links have identical frequencies and contain individual characters encapsulated in control bits, called start/stop bits that designate the beginning and end of each character. Synchronous links try to use the same speed as the other end of a serial link.

Question 7: What are Asynchronous links?
Answer: Asynchronous links send digital signals without timing. Asynchronous links agree on the same speed, but there is no check or adjustment of the rates if they are slightly different. Only 1 byte per transfer is sent.

Question 8: What are the three layers of the Cisco Hierarchical Model?
Answer. The three layers of the Cisco Hierarchical Model are: 1
the access layer
the distribution layer
the core layer

Question 9:  What is the key advantage of using switches?
Answer: When a switch receives a signal, it creates a frame out of the bits that was extracted from that signal. With this process, it gains access and reads the destination address, after which it forwards that frame to the appropriate port. This is a very efficient means of data transmission, instead of broadcasting it on all ports.

Question10: When does network congestion occur?
Answer: Network congestion occurs when too many users are trying to use the same bandwidth. This is especially true in big networks that do not resort to network segmentation.

Question11: What is a Window in networking terms?
Answer: A Window refers to the number of segments that is allowed to be sent from source to destination before an acknowledgement is sent back.

Question 12: What are broadcast domains?
Answer: A broadcast domain defines a group of devices that receive each others' broadcast messages. As with collisions, the more broadcasts that occur on the network, the slower your network will be. This is because every device that receives a broadcast must process it to see if the broadcast is intended for it.

Question 13: What is the difference between a routing protocol and a routed protocol?
Answer: Routing protocols determine how to route traffic to the best location of a routed protocol. Examples of routing protocols are RIP, EIGRP, OSFP, and BGP. Examples of routed protocols are IP and IPX.


Question14: What is a gateway or Router?
Answer: A node that is connected to two or more networks is commonly called as router or Gateway. It generally forwards message from one network to another.

Question15: Define the terms Unicasting, Multicasting and Broadcasting?
Answer: If the message is sent from a source to a single destination node, it is called Unicasting.
If the message is sent to some subset of other nodes, it is called Multicasting.
If the message is sent to all the m nodes in the network it is called Broadcasting.

Question16: What is CRC?
Answer: CRC, is the most powerful of the redundancy checking techniques, is based on binary division.

Question17: What is Checksum?
Answer: Checksum is used by the higher layer protocols (TCP/IP) for error detection

Question18: What is Sliding Window?
Answer: The sliding window is an abstract concept that defines the range of sequence numbers that is the concern of the sender and receiver. In other words, he sender and receiver need to deal with only part of the possible sequence numbers.


Question19: Does a bridge divide a network into smaller segments?
Answer: Not really. What a bridge actually does is to take the large network and filter it, without changing the size of the network

Question20: What is the role of the LLC sublayer?
Answer: The LLC sublayer, short for Logical Link Control, can provide optional services to an application developer. One option is to provide flow control to the Network layer by using stop/start codes. The LLC can also provide error correction.

Question21: What are the different memories used in a CISCO router?
Answer: – NVRAM stores the startup configuration file
– DRAM stores the configuration file that is being executed
– Flash Memory – stores the Cisco IOS.

Question22: What is the function of the Application Layer in networking?
Answer: The Application Layer supports the communication components of an application and provides network services to application processes that span beyond the OSI reference model specifications. It also synchronizes applications on the server and client.

Question23: Difference between the communication and transmission.
Answer: Transmission is a physical movement of information and concern issues like bit polarity, synchronization, clock etc.
Communication means the meaning full exchange of information between two communication media.


Question24: Differentiate User Mode from Privileged Mode in cisco IOS
Answer: User Mode is used for regular task when using a CISCO router, such as to view system information, connecting to remote devices, and checking the status of the router. On the other hand, privileged mode includes all options that are available for User Mode, plus more. You can use this mode in order to make configurations on the router, including making tests and debugging.

Question25: What is 100BaseFX?
Answer: This is Ethernet that makes use of fiber optic cable as the main transmission medium. The 100 stands for 100Mbps, which is the data speed.

Question26: Differentiate full-duplex from half-duplex.
Answer: In full-duplex, both the transmitting device and the receiving device can communicate simultaneously, that is, both can be transmitting and receiving at the same time. In the case of half-duplex, a device cannot receive while it is transmitting, and vice versa.

Question27: What is MAC address?
Answer: The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.

Question28: Difference between bit rate and baud rate.
Answer: Bit rate is the number of bits transmitted during one second whereas baud rate refers to the number of signal units per second that are required to represent those bits. 
Baud rate = (bit rate / N) 
where N is no-of-bits represented by each signal shift.

Question29: What is ICMP?
Answer: ICMP is Internet Control Message Protocol, a network layer protocol of the TCP/IP suite used by hosts and gateways to send notification of datagram problems back to the sender. It uses the echo test / reply to test whether a destination is reachable and responding. It also handles both control and error messages.

Question30: What is MTU?
Answer: MTU stands for Maximum Transmission Unit. It refers to the maximum packet size that can be sent out onto the data line without the need to fragment it.

Question31: What is latency?
Answer: Latency is the amount of time delay that measures the point from which a network device receives a data frame to the time it sends it out again towards another network segment.

Question32: Utilizing RIP, what is the limit when it comes to number of hops?
Answer: The maximum limit is 15 hop counts. Anything higher than 15 indicates that the network is considered unreachable.

Question33: What is a Frame Relay?
Answer:
Frame Relay is a WAN protocol that provides connection-oriented communication by creating and maintaining virtual circuits. It has a high performance rating and operates at the Data Link and Physical Layers.

Question34: What is difference between ARP and RARP?
Answer:
The address resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical address, used by a host or a router to find the physical address of another host on its network by sending an ARP query packet that includes the IP address of the receiver.
The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.

Question 35: What is Proxy ARP?
Answer: It is using a router to answer ARP requests. This will be done when the originating host believes that a destination is local, when in fact is lies beyond router.

Question36: What is the minimum and maximum length of the header in the TCP segment and IP datagram?
Answer:
The header should have a minimum length of 20 bytes and can have a maximum length of 60 bytes.

Question37: Explain the benefits of VLANs.
Answer: VLANs allow the creation of collision domains by groups other than just physical location. Using VLANs, it is possible to establish networks by different means, such as by function, type of hardware, protocol, among others. This is a big advantage when compared to conventional LANs wherein collision domains are always tied to physical location.

Question 38: What is subletting?
Answer: Subletting is the process of creating smaller networks from a big parent network. Being a part of a network, each subnet is assigned some additional parameters or identifier to indicate its subnet number.

Question39: What are the advantages of a layered model in the networking industry?
Answer: A layered network offers many advantages. It allows administrators to make changes in one layer without the need to make changes in the other layers. Specialization is encouraged, allowing the network industry to make progress faster. A layered model also lets administrators troubleshoot problems more efficiently.

Question40: What are some standards supported by the Presentation layer?
Answer: Presentation layer supports many standards, which ensures that data is presented correctly. These include PICT, TIFF and JPEG for graphics, MIDI, MPEG and QuickTime for Video/Audio.

Question41: What is HDLC?
Answer: HDLC is short for High Level Data Link Control protocol, and is a propriety protocol of CISCO. It is the default encapsulation operated within CISCO routers.

Question42: What is Bandwidth?
Answer: Bandwidth refers to the transmission capacity of a medium. It is a measure of how much volume a transmission channel can handle, and is measured in Kbps.

Question43: How does Hold-downs work?
Answer: Hold-downs prevent regular update messages from reinstating a downed link by removing that link from update messages. It uses triggered updates to reset the hold-down timer.

Question44: What are packets?
Answer: Packets are the results of data encapsulation. These are data that has been wrapped under the different protocols of the OSI layers. Packets are also referred to as datagrams.

Question45:What are segments?
Answer: Segments are sections of a data stream that comes from the upper OSI layers and ready for transmission towards the network. Segments are the logic units at the Transport Layer.

Question46: Give some benefits of LAN switching.
Answer: – Allows full duplex data transmission and reception
– media rate adaption
– easy and efficient migration

Question47: What is Route Poisoning?
Answer: Route Poisoning is the process of inserting a table entry of 16 to a route, making it unreachable. This technique is used in order to prevent problems caused by inconsistent updates on a route.

Question48: How do you find valid hosts in a subnet?
Answer: The best way to go about this is to use the equation 256 minus the subnet mask. The hosts that are considered valid are those that can be found between the subnets.

Question49: Why is network segmentation a good idea when managing a large network?
Answer: For a network administration, segmenting a network would help ease network traffic and ensures that high bandwidth is made available at all times for all users. This translates to better performance especially for a growing network.

Question50: Mention what is the difference between the switch, hub?
Answer:


Hub

Switch

Hub has single broadcast domain and collision domain. Anything comes in one port is sent out to the others.

It is a device that filters and forwards packets between LAN segments. Switches have single broadcast domain and multiple collision domains. It supports any packet protocol, as such it operates at the data link layer 2 and layer 3



Question51: Mention what is the size of IP address?
Answer: Size of IP address is 32 bit for IPv4 and 128 bit for IPv6.

Question52: Mention what is DHCP?
Answer: DHCP stands for Dynamic Host Configuration Protocol.  DHCP assigns an IP address automatically to a given workstation client.  You can also make static IPS for machines like printers, servers, routers and scanners.

Question53: Mention what is BOOTP?
Answer: BOOTP is a computer networking protocol used to deploy an IP address to network devices from a configuration server.

Question54: Mention differences betweenTCP and UDP?
Answer:

TCP (Transmission Control Protocol)

UDP (User Datagram Protocol)

TCP is connection oriented protocol. When connection lost during transferring files, the server would request the lost part.  While  transferring a message, there is no corruption while transferring a  message

UDP is based on connectionless protocol. When you send data, there is no guarantee whether your transferred message will reach there without any leakage

The message will deliver in the order it is sent

The message you sent may not be in the same order

Data in TCP is read as a stream, where one packet ends, and another begins

Packets are transmitted individually and are guaranteed to be whole if they arrive

Example of TCP includes World Wide Web, file transfer protocol,   e-mail,

Example for UDP are VOIP (Voice Over Internet Protocol) TFTP ( Trivial File Transfer Protocol),


Question55:  What command do we give if router IOS is stucked?
Answer: Cntrl+Shift+F6 and X is the command we give if router IOS is stucked.

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