CCNA CCNP Interview Questions answers(Part-1)
1.Which layer of the OSI model is responsible for reliable connections?
Answer: The Transport layer of the OSI model is responsible for reliable connections.
2.What is the difference between acknowledgments and handshaking?
Answer: Handshaking is used to negotiate the properties of a connection that is being established. Acknowledgments are used to tell the sender that data has been successfully received by the destination during the use of a connection.
3.How many VTP modes are there and what are they?
Answer: Three: Server, Client, and Transparent
4.What are the two types of Trunk encapsulation protocols?
Answer: IEEE 802.1Q and Cisco’s ISL
5.What are the four primary no routable protocols?
Answer: SNA, NetBIOS, DEC LAT, DEC MOP
6.What is the difference between TCP and UDP?
Answer: The primary difference between TCP and UDP is that TCP is a connection oriented protocol and UDP is a connectionless protocol.
7.What is HSRP?
Answer: HSRP, or the Hot Standby Routing Protocol, is a Cisco proprietary protocol that brings routing functionality to end devices that would otherwise not be capable of taking advantage of redundant network connections. HSRP enables a pair of Cisco routers to work together to present the appearance of a single virtual default-gateway to end devices on a LAN segment.
8.What is the difference between a Public IP address and a Private IP address?
Answer: Public address space is a unique address that is assigned to a company. Private address space is not recognized by the Internet and can be used by anyone within their private network.
9.What does AAA stand for?
Answer: Authentication, authorization, and accounting
10.The H.323 protocol is used for what?
Answer: H.323 is used for multiservice (multimedia) applications, usually in a Voice Over IP environment.
11.What type of routing protocol maintains neighbors?
Answer- Link State
12.what is the range of values for administrative distance?
Answer: 0-255
13.Describe the difference between unicast, multicast, and broadcast traffic?
Answer: Unicast traffic flows from a single source to a single destination MAC address. Multicast traffic flows from a single source MAC address to many destinations and uses a functional MAC address. Broadcast traffic is from a single source to all devices on the Ethernet segment. This is specified by a destination MAC address of all ones.
14.What are the four different Ethernet encapsulation types?
Answer: From the Cisco IPX encapsulation command they are ARPA, NOVELL-ETHER, SAP and SNAP
15.What are the three main tasks of a transparent bridge?
Answer: Learning, Forwarding, Filtering
16.What type of routing protocol is EIGRP?
Answer: Hybrid
17.While troubleshooting a connectivity problem on the network, you issue the ping command from your PC command prompt, but the output shows “request times out.” At which OSI layer is this problem associated with?
Answer: The Network Layer
18.What algorithm does OSPF use to compute its route table?
Answer: OSPF uses the shortest path first (SPF) algorithm, which is also known as the Dijkstra algorithm.
19.What is a stub area?
Answer: A stub area is an area that does not accept routing updates from outside its autonomous system.
20.What does the TTL field of an IP packet header do?
Answer: The TTL field indicates the maximum time that a packet can be on the network. Each router that processes this packet decrements the TTL value by 1. If the value reaches zero, the packet is discarded from the network. The purpose of this field is to eliminate the possibility of a packet endlessly traversing the network.
21.What is the primary purpose of a LAN?
Answer: The primary purpose of a local-area network is to allow resource sharing. The resources may be devices, applications, or information. Examples of shared resources are files, databases, e-mail, modems, and printers.
22.What is a protocol?
Answer: A protocol is an agreed-upon set of rules. In data communications, the rules usually govern a
procedure or a format.
23.What is the purpose of a MAC protocol?
Answer: A Media Access Control protocol defines how a given LAN medium is shared, how LAN devices
connected to the medium are identified, and how frames transmitted onto the medium are
24.What are the three sources of signal degradation on a data link?
Answer: The three sources of signal degradation on a data link are attenuation, interference, and distortion. Attenuation is a function of the resistance of the medium. Interference is a function of noise entering the medium. Distortion is a function of the reactive characteristics of the medium, which react differently to different frequency components of the signal.
25.What is the purpose of a repeater?
Answer: A repeater is a device that extends the useful range of a physical medium by reading a degradedsignal and producing a “clean” copy of the signal.
26.What is the purpose of a bridge?
Answer: A bridge is a device that increases the capacity of a LAN. A bridge divides the data link into
segments, forwarding only traffic that is generated on one segment and is destined for another
segment. By controlling and limiting the traffic on a data link, more devices may be attached to the LAN.
27.What makes a transparent bridge transparent?
Answer: A transparent bridge “listens promiscuously” on each of its ports. That is, it examines all frames on all media to which it is attached. It records the source MAC identifiers of the frames, and the ports on which it learns the identifiers, in a bridging table. It can then refer to the table when deciding whether to filter or forward a frame. The bridge is transparent because it performs this learning function independently of the devices that originate the frames. The end devices themselves have no knowledge of the bridge.
28.Name three fundamental differences between LANs and WANs?
Answer: Three fundamental differences between local-area and wide-area networks are:
LANs are limited to a small geographic area, such as a single building or small campus.
WANs cover a large geographic area, from citywide to worldwide.
LANs usually consist entirely of privately owned components. Some components of a WAN, such as a packet switching network or point-to-point serial links, are usually leased from a service provider.
A LAN provides high bandwidth at a relatively cheap price. The bandwidth across a WAN is significantly more expensive.
29.What is the purpose of a broadcast MAC identifier? What is the broadcast MAC identifier, in hex and in binary?
Answer: A broadcast MAC identifier, when used as the destination address of a frame, signifies that the data is for all devices attached to the data link. In binary, the broadcast MAC identifier is all ones. In hex, it is ffff.ffff.ffff.
30.What is the primary similarity between a bridge and a router? What is the primary difference between a bridge and a router?
Answer: The primary similarity between a bridge and a router is that both devices increase the number of hosts that may be interconnected into a common communications network. The difference is that a bridge works by interconnecting separate segments of a single network, whereas a router interconnects separate networks.
31.What is a packet? What is the primary similarity between a frame and a packet? What is the primary difference between a frame and a packet?
Answer: A packet is the means by which data is transported from one network to another. The similarity between a frame and a packet is that they both encapsulate data and provide an addressing scheme for delivering the data. The difference between a frame and a packet is that the frame delivers data between two devices sharing a common data link, whereas a packet delivers data across a logical pathway, or route, spanning multiple data links.
32.As a packet progresses across an internetwork, does the source address change?
Answer: Neither the source nor the destination address of a packet changes as it progresses from the source of the packet to the destination.
33.What is a network address? What is the purpose of each part of a network address?
Answer: Network addresses are the addresses used in packets. Each network address has a network part, which identifies a particular data link, and a host or node part, which identifies a specific device on the data link identified by the network part.
34.What is the primary difference between a network address and a data link identifier?
Answer: A packet identifies a device from the perspective of the entire internetwork. A frame identifies a device from the perspective of a single data link. Because the connection between two devices across an internetwork is a logical path, a network address is a logical address. Because the connection between two devices across a data link is a physical path, a data link identifier is a physical address.
35.What are the five layers of the TCP/IP protocol suite? What is the purpose of each layer?
Answer: The five layers of the TCP/IP protocol suite are the following:
Physical layer
Data link layer
Internet (or IP) layer
Host-to-host layer
Application layer
36.What is the most common IP version presently in use?
Answer: The most common IP version now in use is version 4.
37.What is fragmentation? What fields of the IP header are used for fragmentation?
Answer: Routers perform fragmentation when a packet is longer than the maximum packet length (Maximum Transmission Unit, or MTU) supported by a data link onto which the packet must be transmitted. The data within the packet will be broken into fragments, and each fragment will be encapsulated in its own packet. The receiver uses the Identifier and Fragment Offset fields and the MF bit of the Flags field to reassemble the fragments.
38.What is the purpose of the TTL field in the IP header? How does the TTL process work?
Answer: The Time to Live (TTL) field prevents “lost” packets from being passed endlessly through the IP internetwork. The field contains an 8-bit integer that is set by the originator of the packet. Each router through which the packet passes will decrement the integer by one. If a router decrements the TTL to zero, it will discard the packet and send an ICMP “time exceeded” error message to the packet’s source address.
39.What is the first octet rule?
Answer: The first octet rule determines the class of an IP address as follows:
Class A: The first bit of the first octet is always 0.
Class B: The first two bits of the first octet are always 10.
Class C: The first three bits of the first octet are always 110.
Class D: The first four bits of the first octet are always 1110.
Class E: The first four bits of the first octet are always 1111.
How are class A, B, and C IP addresses recognized in dotted decimal? How are they recognized inbinary?
Answer: The A, B, C IP addresses are recognized in dotted decimal and binary as follows:
Class Binary Range of First Octet Decimal Range of First Octet
A 0000000 – 01111110 1 – 126
B 10000000 – 10111111 128 – 191
C 11000000 – 11011111 192- 223
40.What is an address mask, and how does it work?
Answer: An IP address mask identifies the network part of an IP address. Each one in the 32-bit mask marks the corresponding bit in the IP address as a network bit. A zero in the mask marks the
Corresponding bit in the IP address as a host bit. A Boolean AND is performed in all 32 bits of the address and the mask; in the result, all network bits of the mask will be repeated, and all host bits will be changed to zero.
41.What is a subnet? Why are subnets used in IP environments?
Answer: A subnet is a sub grouping of a class A, B, or C IP address. Without subletting, the network part of a major class A, B, or C IP address can only identify a single data link. Subnetting uses some of the host bits of a major IP address as network bits, allowing the single major address to be “Subdivided” into multiple network addresses.
42.Why can’t a subnet of all zeros or all ones be used in a classful routing environment?
Answer: A classful routing protocol has no way to differentiate between the all-zeroes subnet and the major IP address, and between the all-ones subnet and the all-hosts, all-subnets broadcast address of the major IP address.
43.What is ARP?
Answer: ARP, or Address Resolution Protocol, is a function that maps the IP addresses of interfaces on a data link to their corresponding MAC identifiers.
44.What is proxy ARP?
Answer: Proxy ARP is a function of an IP router. If the router hears an ARP request, and
The destination network or subnet is in the router’s routing table, and
The table indicates that the destination is reachable via a different router interface than the one on which the ARP request was received, The router will respond to the ARP request with its own MAC address.
45.What is a redirect?
Answer: A redirect is an IP router function. If a device has sent a packet to the router and the router must forward the packet to a next-hop router on the same data link, the router will send a redirect to the originating device. The redirect will inform the device that it can reach the next-hop router directly.
46.What is the essential difference between TCP and UDP?
Answer: TCP, or Transmission Control Protocol, provides a connection-oriented service over the Connectionless internet layer. UDP, or User Datagram Service, provides a connectionless service.
47.What mechanisms does TCP use to provide connection-oriented service?
Answer: Correct sequencing is accomplished with sequence numbers. Reliability is accomplished by using checksums, acknowledgments, timers, and retransmissions. Flow control is accomplished by windowing.
48.Instead of ARP, Novell NetWare uses a network address that includes a device’s MAC address as the host portion. Why can’t IP do this?
Answer: A MAC identifier is a fixed-length binary integer. If IP used MAC identifiers as the host part of the IP address, subnetting would not be possible because there would be no flexibility in using some of the host bits as network bits.
49.NetWare has a transport layer service similar to TCP called Sequenced Packet Exchange (SPX), but no service similar to UDP. Applications requiring connectionless service directly access the connectionless IPX at the network layer. What purpose does UDP serve by providing aconnectionless service on top of what is already a connectionless service?
Answer: The only purpose of the UDP header is to add fields for the source and destination port numbers.
50.What information must be stored in the route table?
Answer: At a minimum, each entry of the routing table must include a destination address and the address of a next-hop router or an indication that the destination address is directly connected.
