Q-1 What type of routing protocol maintains
neighbors?
Answer- Link State
Q-2 what is the range of values for
administrative distance?
Answer: 0-255
Q-3 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.
Q-4 What are the four different Ethernet
encapsulation types?
Answer: From the Cisco IPX encapsulation
command they are ARPA, NOVELL-ETHER, SAP and SNAP
Q-5 What are the three main tasks of a transparent
bridge?
Answer: Learning, Forwarding, Filtering
Q-6 What type of routing protocol is EIGRP?
Answer: Hybrid
Q-7 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
Q-8 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.
Q-9 What is a stub area?
Answer: A stub area is an area that does not
accept routing updates from outside its autonomous system.
Q-10 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.
----------------------------------------------------------------------------------------------------------
1 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.
2: What is a protocol?
A: A protocol is an agreed-upon set of rules. In data
communications, the rules usually govern a
procedure or a format.
3: 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
formatted.
4: What is a frame?
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, anderror-checking information.
5: 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.
6: 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.
7: 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.
8: 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.
9: 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 degradedsignal and producing a "clean"
copy of the signal.
10: 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.
11: 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.
12: 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.
13: 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.
14: What is the primary similarity between a bridge and a router? What
is the primary difference
between a bridge and a
router?
A: 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.
15: 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?
A: 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.
16: As a packet progresses across an internetwork, does the source
address change?
A: Neither the source nor the destination address of a packet
changes as it progresses from the source of the packet to the destination.
17: What is a network address? What is the purpose of each part of a
network address?
A: 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.
18: What is the primary difference between a network address and a
data link identifier?
A: 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.
1: What are the five layers of the TCP/IP protocol suite? What is the
purpose of each layer?
A: 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
CC
2: What is the most common IP version presently in use?
A: The most common IP version now in use is version 4.
3: What is fragmentation? What fields of the IP header are used for
fragmentation?
A: 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.
4: What is the purpose of the TTL field in the IP header? How does
the TTL process work?
A:
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.
5: What is the first octet rule?
A: 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.
6: How are class A, B, and C IP addresses recognized in dotted
decimal? How are they recognized inbinary?
A: 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
7: What is an address mask, and how does it work?
A: 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.
8: What is a subnet? Why are subnets used in IP environments?
A: 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.
9: Why can't a subnet of all zeros or all ones be used in a classful
routing environment?
A: 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.
10: What is ARP?
A: ARP, or Address Resolution Protocol, is a function that maps the
IP addresses of interfaces on a data link to their corresponding MAC
identifiers.
11: What is proxy ARP?
A: 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.
12: What is a redirect?
A: 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.
13: What is the essential difference between TCP and UDP?
A: TCP, or Transmission Control Protocol, provides a
connection-oriented service over the
Connectionless
internet layer. UDP, or User Datagram Service, provides a connectionless
service.
14: What mechanisms does TCP use to provide connection-oriented
service?
A: Correct sequencing is accomplished with sequence numbers.
Reliability is accomplished by using checksums, acknowledgments, timers, and
retransmissions. Flow control is accomplished by windowing.
15: 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?
A: 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.
16: 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?
A: The only purpose of the UDP header is to add fields for the source
and destination port numbers.
1: What information must be stored in the route table?
A: 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.
2: What does it mean when a route table says that an address is
variably subnetted?
A: Variably subnetted means
that the router knows of more than one subnet mask for subnets of the same
major IP address.
3: What are discontiguous subnets?
A: Discontiguous subnets are two or more subnets of a major IP
network address that are separated by a different major IP address.
4: What command is used to examine the route table in a Cisco router?
A: show ip route is used to examine the
routing table of a Cisco router.
5: What are the two bracketed numbers associated with the
non-directly connected routes in the route table?
A: The first bracketed number is the administrative distance of the
routing protocol by which the route was learned. The second number is the
metric of the route.
6: When static routes are configured to reference an exit interface
instead of a next-hop address, in what way will the route table be different?
A: When a static route is configured to reference an exit interface
instead of a next-hop address, the destination address will be entered into the
routing table as directly connected.
7: What is a summary route? In the context of static routing, how are
summary routes useful?
A: A summary route is a single route entry that points to multiple
subnets or major IP addresses. In the context of static routes, summary routes
can reduce the number of static routes that must be configured.
8: What is an administrative distance?
A: An administrative distance is a rating of preference for a
routing protocol or a static route. Every routing protocol and every
static route has an administrative distance associated with it. When a router
learns of a destination via more than one routing protocol or static route, it
will use the route with the lowest administrative distance.
9: What is a floating static route?
A: A floating static route is an alternative route to a
destination. The administrative distance is set high enough that the floating
static route is used only if a more-preferred route becomes unavailable.
10: What is the difference between equal-cost and unequal-cost load
sharing?
A: Equal-cost load sharing distributes traffic equally among
multiple paths with equal metrics.
Unequal-cost load
sharing distributes packets among multiple paths with different metrics. The
traffic will be distributed
inversely proportional to the cost of the routes.
11: How does the switching mode at an interface affect load sharing?
A: If an interface is fast switched, per destination load sharing
is performed. If an interface is process switched, per packet load sharing is
performed.
12: What is a recursive table lookup?
A: A recursive routing table lookup occurs when a router cannot
acquire all the information it needs to forward a packet with a single routing
table lookup. For example, the router may perform one lookup to find the route
to a destination and then perform another lookup to find a route to the next
hop router of the first route.
1: What is a routing protocol?
A: A routing protocol is a "language" that routers speak
to each other to share information about
network destinations.
2: What basic procedures should a routing algorithm perform?
A: At a minimum, a routing protocol should define procedures for:
Passing reachability
information about networks to other routers
Receiving reachability
information from other routers
Determining optimal
routes based on the reachability information it has and for recording
this information in a
route table
Reacting to,
compensating for, and advertising topology changes in an internetwork
3: Why do routing protocols use metrics?
A: A route metric, also called a route cost or a route distance, is
used to determine the best path to a destination. Best is
defined by the type of metric used.
4: What is convergence time?
A: Convergence time is the time a group of routers take to complete
the exchange of routing
information.
5: What is load balancing? Name four different types of load
balancing.
A: Load balancing is the process of sending packets over multiple
paths to the same destination. Four types of load balancing are:
Equal cost, per packet
Equal cost, per
destination
Unequal cost, per packet
Unequal cost, per
destination
6: What is a distance vector routing protocol?
A: A distance vector protocol is a routing protocol in which each
router calculates routes based on the routes of its neighbors and then passes
its routes to other neighbors.
7: Name several problems associated with distance vector protocols.
A: Several problems associated with distance vector protocols are:
A susceptibility to
incorrect routing information because of its dependence on neighbors for
correct information
Slow convergence
Route loops
Counting to infinity
8: What are neighbors?
A: Neighbors are routers connected to the same data link.
9: What is the purpose of route invalidation timers?
A: Route invalidation timers delete routes from a route table if
they exceed a certain age.
10: Explain the difference between simple split horizon and split
horizon with poisoned reverse.
A: Simple split horizon does not send route information back to the
source of the route information. Split horizon with poisoned reverse sends the
information back to the source but sets the metric to unreachable.
No comments:
Post a Comment