Top Interview Questions:
- Which layer of the OSI model is responsible for reliable
connections?
Answer: The Transport layer of the OSI model is responsible
for reliable connections.
- 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.
- How many VTP modes are there and what are they?
Answer: Three: Server, Client, and Transparent
- What are the two types of Trunk encapsulation protocols?
Answer: IEEE 802.1Q and Cisco’s ISL
- What are the four primary no routable protocols?
Answer: SNA, NetBIOS, DEC LAT, DEC MOP
- 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.
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.
- 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.
Answer: Authentication, authorization, and accounting
- The H.323 protocol is used for what?
Answer: H.323 is used for multiservice (multimedia)
applications, usually in a Voice Over IP environment.
- What type of routing protocol maintains neighbors?
Answer- Link State
- what is the range of values for administrative distance?
Answer: 0-255
- 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.
- What are the four different Ethernet encapsulation types?
Answer: From the Cisco IPX encapsulation command they are ARPA,
NOVELL-ETHER, SAP and SNAP
- What are the three main tasks of a transparent bridge?
Answer: Learning, Forwarding, Filtering
- What type of routing protocol is EIGRP?
Answer: Hybrid
- 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
- 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.
- What is a stub area?
Answer: A stub area is an area that does not accept routing updates from
outside its autonomous system.
- 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.
- What is the primary purpose of a LAN?
A: 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.
A: A protocol is an agreed-upon set of rules. In data
communications, the rules usually govern a
procedure or a format.
- What is the purpose of a MAC protocol?
A: 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
A: A frame is a digital “envelope” that provides the
information necessary for the delivery of data across a data link. Typical
components of a frame are identifiers (addresses) of the source and destination
devices on the data link, an indicator of the type of data enclosed in the
frame, and error-checking information.
- What feature is common to all frame types?
A: A feature common to all frame types is a format for
identifying devices on the data link.
- What is a MAC address or MAC identifier?
A: A Media Access Control address or identifier is a
means by which individual devices connected to a data link are uniquely
identified for the purpose of delivering data.
- Why is a MAC address not a true address?
A: An address specifies a location. A MAC address is
not a true address because it is permanently associated with the interface of a
specific device and moves whenever the device moves. A MAC identifies the
device, not the location of the device.
- What are the three sources of signal degradation on a data
link?
A: 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.
- What is the purpose of a repeater?
A: A repeater is a device that extends the useful range
of a physical medium by reading a degraded signal and producing a “clean” copy
of the signal.
- What is the purpose of a bridge?
A: 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.
- What makes a transparent bridge transparent?
A: 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.
- Name three fundamental differences between LANs and WANs.
A: 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.
- What is the purpose of a broadcast MAC identifier? What is the
broadcast MAC identifier, in hex and in binary?
A: 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.
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