CCNA 3 Exploration Chapter 1 Study Questions

8/12/2019 CCNA 3 Exploration Chapter 1 Study Questions

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CCNA 3 Exploration Chapter 1 Study Questions

1.1 Switched LAN Architecture

1) What are the three layers of the hierarchical network design model?

Access, distribution and core.

2) What are the advantages of designing LANs using the hierarchical model?

The hierarchical model separates out different functions of a network, giving a modulardesign. This should make the network easier to manage and troubleshoot. It should beeasier to expand the network (scalability), and it should be easier to maximise

performance.

3) What is the purpose of the access layer?

It allows end devices to connect to the network and controls which devices mayconnect.

4) What sorts of devices are found at the access layer?

End devices, such as PCs, printers, and IP phones. Network devices such as routers,switches, bridges, hubs, and wireless access points.

5) What is the purpose of the distribution layer?

It controls the flow of network traffic. In particular, it controls traffic between differentbroadcast domains (subnetworks, VLANs). It aggregates traffic from the access layerthat needs to be passed to the core layer for longer distance transmission.

6) What sorts of devices are found at the distribution layer?

High-performance switches. They should have high availability and redundancy toensure reliability

7) What is the purpose of the core layer?

It is the high speed backbone of the network. Its main task is to forward large amountsof data quickly.

8) What is a collapsed core model and where might it be used?

The distribution layer and the core layer are combined. It is used for smaller networks.


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9) What is a wiring closet?

A room designed to hold network devices such as switches and routers. It is a centralpoint where network cabling comes together.

10) Why is it not easy to see the logical hierarchical design of a network whenlooking at the network layout in a building?

The devices operating at different layers may not be physically separated. For example,switches operating at different layers may be kept in the same cabinet.

11) Why is redundancy important in a network?

It gives better availability and reliability. If one switch or link goes down then analternative path can be used.

12) Which layers normally have redundancy built in?

Core and distribution layers.

13) How can the hierarchical design help to give high performance?

Traffic (and particularly long distance traffic) is forwarded through distribution layer andcore layer switches that are designed to work at high speeds, and not through a seriesof lower-speed access layer switches.

14) How can switches at the different layers contribute to network security?

Access layer switches can restrict the devices that are permitted to connect to theirports. Distribution layer devices can be configured with access control policies thatrestrict traffic according to IP addresses or application layer protocols. (The core layer isoptimised for speed. Security measures are not appropriate at this layer because theyslow things down.)

15) How does a hierarchical design help to make a network manageable?

Switches at a given layer have similar functions and therefore are likely to have similarconfigurations. This makes it easier to check configurations and to configure newswitches.

16) Should the same type of switch be used at each layer of the hierarchicaldesign?

No. The distribution and core layers need very fast switches. The access layer can useless expensive switches.


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17)What is network diameter in hierarchical network design?

Network diameter is the number of devices that a packet has to cross before it reachesits destination.

18) What is network device latency?

Network device latency is the time spent by a device as it processes a packet or frame.

19) What sort of processing does a switch have to do on each packet?

The switch has to look in the frame header and find the destination MAC address. Itthen looks this address up in its MAC address table and finds the matching exit port. Itthen forwards the frame out of the port.

20) How can bandwidth aggregation be implemented?

Switches can be linked by more than one physical link. These physical links can becombined into one logical link that makes use of the combined bandwidth.

21) Why is redundancy not normally provided at the access layer?

It would be too expensive. The advantage of improved reliability would not justify theextra cost.

22) When designing a new network, at which layer would you start?

At the access layer. Make sure that all end devices will be able to connect to thenetwork.

23) What is a converged network?

A network that carries voice, video and data.

24) What factors have slowed the move towards converged networks?

Converged networks need special switching equipment that was originally affordableonly by big companies.Converged networks need Quality of Service management to give voice and videotraffic priority over data.Converged networks need people with expertise to set them up and manage them.Where firms have existing separate networks that work well, the firms may be reluctantto make a change.


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30) Which two types of traffic need to be considered when planning data storagefacilities?

Client-server traffic and server-server traffic.

31) How can server-server traffic be optimised?

Servers and data stores should be kept physically close to each other and should beconnected by high performance switches. Businesses often keep their servers and datastores in a secure data centre.

32) How might you deal with a bottleneck where there is insufficient bandwidth?

Use link aggregation (multiple links between switches) or install higher performanceswitches.

33) Why is it important to produce a topology diagram as part of the networkdesign process?

It is difficult to produce a topology diagram later by examining the network itself, and thediagram is necessary for the efficient management of the network. It shows all theswitches and how they are connected, including aggregated links and redundant links,and the ports used. It shows how servers, storage devices and end user devices suchas workstations are connected.

34) How is the thickness of a switch (top to bottom) measured?

In rack units (U).

35) What is the difference between a fixed configuration switch and a modularswitch?

A fixed configuration switch has a fixed number of ports and these cannot be changed.A modular switch has a chassis that can take line cards. The line cards contain theports. A modular switch can therefore have different numbers or types of ports,depending on the choice of line cards.

36) What are stackable switches?

Stackable switches are designed to be connected together and act as a single switch.The connection between the switches is through a special high speed port and notthrough the normal switch ports.


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37) What is the port density of a switch?

The number of available access ports.

If 80 outlets need to be connected to a switch, why is a single large modular switch

likely to be a better choice than four fixed configuration switches with 24 ports each?

The four switches each need their own power supply, and they use ports to connect toeach other. They may need several ports for each link if aggregation is needed. Thesingle large switch needs a single power supply. No ports are needed for internal links,and the switchs internal backplane provides a higher speed connection than linksbetween switches.

38) What is wire speed, and what is forwarding rate?

Wire speed is the data rate that a switch port can attain. A port may be designed to

operate at 100 Mb/s Fast Ethernet or 1000 Mb/s Gigabit Ethernet. The forwarding rateis the amount of data that the switch can process per second. If the forwarding rate isless than the total wire speed of all the ports then it is not possible for all the ports tooperate simultaneously at their wire speed.

39) What is Etherchannel?

A system that uses link aggregation to provide high bandwidth between switches. Up to8 ports can be bound together so that they act as a single link.

40) What is PoE and what are its advantage and disadvantage?

Power over Ethernet is a feature that lets a switch provide a power supply to a devicesuch as an IP phone or a wireless access point. The power is supplied over theEthernet cable. The advantage is that the devices do not need a separate power supply,so it may be possible to position them more flexibly. The disadvantage is that thefeature makes the switch much more expensive.

41) At which OSI layer to typical traditional switches operate?

Layer 2.

42) What is a multilayer switch?

A switch that operates at layer 3 as well as at layer 2. For example, it can forwardpackets based on IP addressing, not just on MAC addressing.


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43) What features are required for access layer switches?

Port security, VLANs, Fast Ethernet/Gigabit Ethernet, PoE, and link aggregation. Qualityof Service is needed for converged networks.

44) What features are required for distribution layer switches?

High forwarding rate to allow all ports to operate to their full bandwidthHigh bandwidth links (possibly 10Gbps) and link aggregationRedundancy to ensure reliability and availabilityMultiple, hot-swappable power suppliesQuality of service to maintain priority for video and voice trafficInter-VLAN routing (layer 3 function)

Access control lists for security (layer 3 function)

45) What features are required for core layer switches?

Very high forwarding rates as this is the high speed backbone of the network.High bandwidth ports, preferably 10Gbps. Support for link aggregation.Redundancy to give reliability and availability.Redundant power supplies.Efficient cooling.Hot-swappable hardware components to avoid downtime for maintenance.Support for quality of service. (Particularly important where there are links to lowerbandwidth WANs.)Layer 3 features.

46) Which Cisco Catalyst switch does not provide a command line interface?

Catalyst Express 500

47) Which Catalyst switch is suitable for access level use in small organisations,provides up to 48 ports, but does not provide PoE?

Catalyst 2960

48) What does the Catalyst 3560E switch provide that the 3560 switch does not?

10 Gbps connectivity.

49) Which catalyst switch has forwarding rates up to 720 Gbps?

Catalyst 6500


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50) Which type of catalyst switch can be stacked so that up to 9 switches canoperate as a single logical switch?

Catalyst 3750

51) What is special about the Catalyst 4900 series switches?

They are designed for use in data centres for linking servers and data stores.

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CCNA 3 Exploration Chapter 1 Study Questions