OSI
(ISO) International organization for standardization
ISO has designed a reference model called osi reference model (open system interconnection).
It has 7 layers. It says that Any n/w for communication needs 7 layers
7.Application layer:
The user uses application layer to send the data. The protocols@ this layer are ftp, http, SMTP (e-mail) telnet etc.
6. Presentation layer:
Presentation layer takes the data from application layer and presenting different formats for securing reason. The services offered @This layer are Compression – decompression Coding – decoding Encryption - decryption
5. Session layer:
Establishing the session or the connectivity n/w 1 & n/w 2 is done By the session layer. It 1. Establishes a session 2. Maintains it & 3. Terminates it b/w the application
4. Transport layer:
End-end connectivity during a session b/w two application is done By the transport layer. It also decides the type of connection like tcpor udp i.e. connection oriented or connection less. Services: Sequencing Flow ctrl, error detection & correction Transport layer info + data is called segment
3. Network layer:
Logical addressing is done at the network layer i.e. source address &destination address are attached to the data. Protocols @network layer Routed protocols routing protocols
Routed protocols: they always carry the data along with them ex: ip, ipx
Routing protocol: they identify the path for routed protocol to carry the data At this layer routers & layer 3 switches forms packets. eg: rip,igrp,ospf
2. Data link layer:
It has two Sub layers a)MAC{Media access control } b) LLC {logical link control framing of data}Ip address is lik the pin code & MAC address is like house number. Here layer2 switches are used.Wab protocols used at this layer are PPP, HDLC, FP, X.25 etc.Here error checking CRC bits are added to the packets info+ packets --> frames
1. Physical layer:
Takes care of physical connectivity i.e. connector, cable etc. here Frames are converted to bits (1’s & 0’s).The devices like hubs, repeaters, cables & connectors are used at this layer
1: What is the definition of a network?
** A network is a system of lines or channels that cross or interconnect, or a group or system of electrical components and connecting circuitry designed to function in a specific manner.
2: What are network models?
** Network models provide the guiding principles behind the development of network standards.
3: What is a network standard, and why are there network standards?
** Network standards define the rules of network communication and are like laws that must be followed for different equipment vendors to work together.
4: What is a proprietary feature?
** If a vendor implements a feature that does not adhere to any network standards, it is called a proprietary feature.
5: What are the three data transmission modes, and how do they operate?
** Simplex mode, half-duplex mode, and full-duplex mode. Simplex mode is one-way communication only. Half-duplex mode is two-way communication, but not at the same time. Full-duplex mode is simultaneous two-way communication.
6: List the major characteristics of a LAN.
** The primary characteristic of a LAN is its geographic coverage. LANs are found in a small geographic area where there is a short distance between connected computers, as in small offices or on each floor of a larger office building. LANs enable the sharing of office resources, such as file servers for file sharing among users or print servers for shared printers.
7: List the major characteristics of a MAN.
** MANs are found in a metropolitan, or citywide, geographic area, interconnecting two or more office buildings in a broader geographic region than a LAN would support, but not so broad that a WAN would be required.
8: List the major characteristics of a WAN.
** WANS are found in broad geographic areas, often spanning states and countries, and are used to connect LANs and WANs together.
9: What are the three parts of a frame? What is a function of each part?
** Header, data (or payload), trailer. The header is the beginning of the frame, significant in that the frame's source and destination are found in the frame header. The payload is the data part of the frame, the user's information. The trailer identifies the end of the frame.
10: What function in a network does cabling provide?
* Cabling provides the physical interconnection between network devices and nodes.
11: List some examples of user data.
** Examples of user data include e-mail, web-browsing traffic, word-processed documents, spreadsheets, database updates.
12: What is the best definition of network topology?
** Network topology refers to the physical or logical geometric arrangement of interconnected network devices.
13: What is the best definition of network protocol?
** A network protocol is the communication rules and formats followed by all interconnected devices on a network requiring communication with one another.
14: What is the definition of network media?
** Network media refers to the physical component of a network. Communication signals traverse network media from source to destination. Some examples of network media are copper and fiber-optic cabling.
15: What is a network origination point?
** A network connection has two ends: the origination and termination points. The origination point is the source of the data—the location from which the data is being sent.
16: What is a network termination point?
** A network connection has two ends: the origination and termination points. The termination point is the destination of the data—the location to which the data is being sent.
(ISO) International organization for standardization
ISO has designed a reference model called osi reference model (open system interconnection).
It has 7 layers. It says that Any n/w for communication needs 7 layers
7.Application layer:
The user uses application layer to send the data. The protocols@ this layer are ftp, http, SMTP (e-mail) telnet etc.
6. Presentation layer:
Presentation layer takes the data from application layer and presenting different formats for securing reason. The services offered @This layer are Compression – decompression Coding – decoding Encryption - decryption
5. Session layer:
Establishing the session or the connectivity n/w 1 & n/w 2 is done By the session layer. It 1. Establishes a session 2. Maintains it & 3. Terminates it b/w the application
4. Transport layer:
End-end connectivity during a session b/w two application is done By the transport layer. It also decides the type of connection like tcpor udp i.e. connection oriented or connection less. Services: Sequencing Flow ctrl, error detection & correction Transport layer info + data is called segment
3. Network layer:
Logical addressing is done at the network layer i.e. source address &destination address are attached to the data. Protocols @network layer Routed protocols routing protocols
Routed protocols: they always carry the data along with them ex: ip, ipx
Routing protocol: they identify the path for routed protocol to carry the data At this layer routers & layer 3 switches forms packets. eg: rip,igrp,ospf
2. Data link layer:
It has two Sub layers a)MAC{Media access control } b) LLC {logical link control framing of data}Ip address is lik the pin code & MAC address is like house number. Here layer2 switches are used.Wab protocols used at this layer are PPP, HDLC, FP, X.25 etc.Here error checking CRC bits are added to the packets info+ packets --> frames
1. Physical layer:
Takes care of physical connectivity i.e. connector, cable etc. here Frames are converted to bits (1’s & 0’s).The devices like hubs, repeaters, cables & connectors are used at this layer
1: What is the definition of a network?
** A network is a system of lines or channels that cross or interconnect, or a group or system of electrical components and connecting circuitry designed to function in a specific manner.
2: What are network models?
** Network models provide the guiding principles behind the development of network standards.
3: What is a network standard, and why are there network standards?
** Network standards define the rules of network communication and are like laws that must be followed for different equipment vendors to work together.
4: What is a proprietary feature?
** If a vendor implements a feature that does not adhere to any network standards, it is called a proprietary feature.
5: What are the three data transmission modes, and how do they operate?
** Simplex mode, half-duplex mode, and full-duplex mode. Simplex mode is one-way communication only. Half-duplex mode is two-way communication, but not at the same time. Full-duplex mode is simultaneous two-way communication.
6: List the major characteristics of a LAN.
** The primary characteristic of a LAN is its geographic coverage. LANs are found in a small geographic area where there is a short distance between connected computers, as in small offices or on each floor of a larger office building. LANs enable the sharing of office resources, such as file servers for file sharing among users or print servers for shared printers.
7: List the major characteristics of a MAN.
** MANs are found in a metropolitan, or citywide, geographic area, interconnecting two or more office buildings in a broader geographic region than a LAN would support, but not so broad that a WAN would be required.
8: List the major characteristics of a WAN.
** WANS are found in broad geographic areas, often spanning states and countries, and are used to connect LANs and WANs together.
9: What are the three parts of a frame? What is a function of each part?
** Header, data (or payload), trailer. The header is the beginning of the frame, significant in that the frame's source and destination are found in the frame header. The payload is the data part of the frame, the user's information. The trailer identifies the end of the frame.
10: What function in a network does cabling provide?
* Cabling provides the physical interconnection between network devices and nodes.
11: List some examples of user data.
** Examples of user data include e-mail, web-browsing traffic, word-processed documents, spreadsheets, database updates.
12: What is the best definition of network topology?
** Network topology refers to the physical or logical geometric arrangement of interconnected network devices.
13: What is the best definition of network protocol?
** A network protocol is the communication rules and formats followed by all interconnected devices on a network requiring communication with one another.
14: What is the definition of network media?
** Network media refers to the physical component of a network. Communication signals traverse network media from source to destination. Some examples of network media are copper and fiber-optic cabling.
15: What is a network origination point?
** A network connection has two ends: the origination and termination points. The origination point is the source of the data—the location from which the data is being sent.
16: What is a network termination point?
** A network connection has two ends: the origination and termination points. The termination point is the destination of the data—the location to which the data is being sent.
**:Connectionless networking
refers to transferring data in independent units referred to as packets,
without the need to predefine the path of data flow. Instead, the packets are
forwarded using a hop-by-hop routing paradigm between the source and
destination.
18:
Why is
routing needed in a connectionless networking environment? List two means by
which routers obtain information for routing packets toward their destinations.
**:The packets used in connectionless transfer of data have
addressing
information for their intended destination in packet headers. Routing is
needed
to provide information for forwarding packets along optimal paths to
their
target desti-nations.
Various
mechanisms exist for forwarding packets on Cisco routers. However, forwarding
decisions ultimately are based on information in the routing table, which is
populated manually with static routes or dynamically by routing protocols.
19: What
is the difference between functionalities of Interior Gateway Protocols (IGPs)
versus exterior gateway protocols (EGPs)
**:IGPs
exchange routes between routers belonging to a single network domain. EGPs
support routing between domains.
20:
List the two
main groups of IP routing protocols based on the method of operation and
routing algorithm. Also, list two examples of each type.
**:Distance vector and link-state
protocols. RIP and Cisco IGRP are distance vector-based; OSPF and Integrated
IS-IS are link-state protocols. EIGRP falls under yet a third group, called
advance distance vector protocols.
**:
Link-state routing protocols share and collect network topology information by
means of link-state advertisements. Link-state information is stored in a
database, which is fed as input to the shortest path algorithm for determining
the best routes.
22:
What is the
key difference between classless and classful routing protocols? Give an
example of each.
**:Classful protocols operate
under the notion of the rigid boundaries of classful addressing, whereas
classless protocols are more flexible in this, regarding allowing them to
support VLSMs and CIDR.
RIP
is an example of a classful routing protocol. OSPF is an example of a classless
protocol.
**:The concept of administrative
distance is used to distinguish between routing sources and assign relative
preferences between them.
**:The administrative distance of IS-IS
is 115; the administrative distance of OSPF is 110.
25:
If a router
is running both OSPF and IS-IS protocols and has the same route from each of
them, which protocol's information will be used in the IP routing table?
**:The lower administrative
distance is preferred, so only the OSPF route will make it into the IP routing
table.
**: The maximum metric is 15 because RIP was designed for small
networks.
**: RIP is a classful protocol, so it
summarizes the update at the major network boundary.
**:When
RIP sends the update, it checks to see whether the network being adver-tised
has the same mask. If the advertised network has a different mask, RIP doesn't
advertise that network.
30:What transport protocol and port
number do RIP use for sending updates?
**:RIP uses UDP port 520 to transport
its update packets.
**:Split horizon is used in RIP
to avoid routing loops.
32:Does RIP Version 2 solve the discontiguous network problem by
default?
**:No, the command no auto-summary is needed under router rip.
**:No, RIP Version 2 uses a multicast
address of 224.0.0.9 to send its routing updates.
**:RIP
Version 1 does not support authentication, but RIP Version 2 does support it.
35:What is the default update
timer period for IGRP?
**:The default update timer period is
90 seconds.
36:What variables does IGRP use
to calculate its metrics by default?
**:
By default,
IGRP considers only the bandwidth and the delay of the link when calculating
its metrics.
37:What are the K values in the
IGRP metric equation?
**:The
K1 through K5 variables are constant numbers used in the IGRP metric equation.
The default value of the K values are K1 = K3 = 1, K2 = K4 = K5 = 0. The
network administrator can change the default K value to other numbers so that
other components of the metric equation, such as load and reliability, can be
used; however, such a change is highly not recommended.
38:What command is used in IGRP
to perform unequal-cost load balancing?
**:IGRP uses the variance
command to perform unequal-cost load balancing.
39:
What is
split horizon? Does IGRP support this feature?
**:Split horizon, supported by IGRP, is the technique used to avoid
routing loops. With split horizon, the router does not advertise a route over
the interface in which the route is learned from.
**: Because IGRP does not send subnet
mask information as part of the routing update, IGRP does not support VLSM.
41:What is the difference
between metric calculations in IGRP versus EIGRP?
**:The
EIGRP metric is the IGRP metric multiplied by 256.
42:What is an EIGRP query, and
what is it used for?
**:An EIGRP query is sent when
the successor is gone and the feasible successor is not available. An EIGRP
query is used so that EIGRP can have fast convergence.
**:Active routes are routes in
which the primary path is gone and no feasible successors are available. The
router is actively searching for an alternate path.
**:A feasible successor is an
EIGRP neighbor that does not satisfy the feasible condition. Feasible
successors can also be thought of as EIGRP backup routes that are used when the
primary route is gone.
**:EIGRP's multicast address is
224.0.0.10.
**:
The feasible
condition is a condition in which the reported distance is less than the
feasible distances. This condition ensures a loop-free topology.
**:Stuck
in active is a condition in which the router has sent out queries for a lost
route and has not received a reply within the active timer. By default, the
active timer is three minutes.
**:OSPF has five types of
packets.
**:External LSAs have a
Forwarding Address field.
50:Which of the LSA(s) are not
allowed in a totally stubby area?
**:External and summary LSAs are
not allowed in a totally stubby area.
51:What is the multicast address
for All SPF Routers?
**:224.0.0.5 is the multicast
address.
52:Which of the OSPF protocol
packets is used to elect a master and a slave?
**:Type 2 DBD packets are used
to elect a master and a slave.
**:Link-state update packets implement
flooding of the LSA.
54:What is the time limit in
seconds before an LSA is declared as MAXAGED?
**:The limit is 3600 seconds.
**:A common LSA header is 20
bytes long.
56:Name the three network layer
protocols that form the basis of ISO connectionless network services.
**:CLNP, ES-IS, and IS-IS.
57:How many levels are there in
the routing hierarchy supported by the IS-IS routing protocol?
**:ISO 10589 specifies two
levels: Level 1 and Level 2.
**:All IS-IS packets consist of
a header to which special routing information fields, known as TLVs, are
appended.
59:What does the acronym NSAP
stand for, and what is it used for?
**:NSAP stands for network service
access point. NSAPs are network layer address OSI nodes running the CLNP
protocol.
60:
What are the
three major components of an NSAP? Describe the significance of each.
**:
The three
components are area ID, system ID, and N-selector. The area ID defines the area
that the node belongs to, the system ID is a unique address of the node within
its area, and the N-selector specifies a network service user. A 0 value
specifies the routing layer.
61:
What is the
maximum length of an NSAP, and what is the minimum length that can be
configured on a Cisco router?
**:
The maximum
length of an NSAP is 160 bits, or 20 bytes. The minimum size that can be
configured on a Cisco router is 8 bytes. The 8 bytes include 1 byte of
N-selector, 6 bytes of system ID, and 1 byte of area ID.
**:
Link-state
protocols such as IS-IS require each router in an area to have the same view of
the area's topology. Each router creates a link-state packet that describes its
immediate environment shared with other routers in the area. LSPs are collected
in the link-state database. When pieced together, the LSPs in an area's
link-state database describe the topology of the entire area.
63:
What is the
basic difference between Level 1 and Level 2 link-state databases?
**:
A Level 1
link-state database describes a single IS-IS area and contains only LSPs from
the routers in that area. The Level 2 database describes the interconnection
between areas in the IS-IS domain and contains LSPs from the Level 2 routers.
The Level 2 LSPs are intended to provide inter area information.
64:How are flooding and database synchronization different
between a point-to-point link and a broadcast link?
**: LSPs are flooded reliably with
acknowledgments on point-to-point links, whereas they are not acknowledged on
broadcast links. Database synchronization occurs on broadcast media through the
designated router, which sends periodic CSNPs over the link to assist with
synchronization.
65:
Describe the
two steps for enabling basic IS-IS routing on a cisco router.
**:
First, an
IS-IS routing process is configured with the router isis [tag] command. Then,
IS-IS routing is enabled on the relevant interfaces with the ip router isis
[tag] interface-level command.
66:List some show commands that
you can use to verify configuration and operation of IS-IS
**:show clns neighbors, show
clns interface, show isis topology, and show is-is database.
**:
Unicast
packets are destined for only one host. Broadcast packets are destined for all
hosts on the same segment, regardless of whether the host is interested in the
packet. Multicast packets are sent with one copy, and only hosts that are
interested in the multicast packet process the packet.
**:
PIM dense
mode and PIM sparse mode are the two modes.
69:What mechanism does PIM dense mode operate on?
**:
PIM dense
mode operates on the flood-and-prune mechanism. The router first floods the
multicast packets on all interfaces, and the neighbors that don't want the
multicast packet prune the interface.
**:
PIM sparse
mode operates on the prune-and-join mechanism. The router won't forward the
multicast packet until it receives a PIM join on the interface.
71:
What is the
difference between IGMP version 1 and version 2 concerning the group leave
mechanism?
**:
IGMP version
1 doesn't have a specific group leave mechanism. IGMP version 1 group members
simply leave the group silently. IGMP version 2 has a specific group leave
mechanism in which the host sends a specific IGMP leave message to the router
indicating that it's leaving the multicast group.
**:224.0.0.1 is used.
**:
When a
router receives a multicast packet on an interface, it checks its routing table
on the source address of the multicast packet. If the routing table corresponds
with the interface from which the multicast packets are received, RPF check
succeeds and packets are forwarded; otherwise, multi-cast packets are silently
discarded.
**:The rendezvous point (RP) is
where the multicast sender and receiver meet first before the shortest-path
tree is established.
75:
Does BGP
have its own transport mechanism to ensure the guarantee of BGP updates?
a.
BGP has its own transport mechanism to deliver BGP packets to its neighbors.
b.
UDP is a preferred method because BGP neighbors are in most cases directly
connected and the loss of packets is unlikely.
c.
BGP uses TCP as its transport mechanism.
76: Assuming
no Route-Reflection or Confederations are used, what problems might occur if
IBGP neighbors are not fully meshed?
a.
An IBGP update will not be propagated to BGP routers in the AS because the IBGP
learned update is not announced to other IBGP neighbors.
b.
Everything will run fine.
c.
Only external BGP neighbors won't receive the BGP updates.
**:A.
An IBGP update will not be propagated to BGP routers in the AS because the IBGP
learned update is not announced to other IBGP neighbors.
77: What
BGP technique is used to penalize flapping of BGP routes in some other AS?
a.
Route-Reflection
b.
Dampening
c.
Peer groups
78:
The BGP
process can exchange updates with its neighbors after passing which neighbor
state?
a.
Established
b.
Open Sent
c.
Active
79:
Which of the
following techniques are used in solving the IBGP full mesh requirement?
a. Dampening
b. Aggregation
c. Route
Reflection and Confederation
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