CompTIA Network+ Certification Study Guide part 37 ppsx

The network Exam warning NAT hides the local internal IP addresses from external Internet users, which provides a layer of security to your network... To send data to the correct locatio

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identifiers of a number of private hosts to be multiplexed into the transport identifiers of a single global IP address PAT allows numerous hosts from the internal network to share a single external network IP address The advan-tage of this type of translation is that only one global IP address is needed, whereas with NAT, each internal host must translate to a unique external

IP address PAT can be particularly useful for locations or users connected via cable modem, digital subscriber line (DSL), or other similar arrangement wherein they are provided a single global, public IP address In such sce-narios, all inside addresses are translated to this single address

SuMMAry oF ExAM oBJECTIvES

Understanding TCP/IP from the ground up is required to effectively manage

a network whether LAN or WAN TCP/IP is a suite of protocols originally developed by the Department of Defense in a project called the Advanced Research Projects Agency (DARPA) The first WAN implemented using these protocols was called the Advanced Research Projects Agency Network (ARPANET) It was during this time that TCP/IP was designed and developed

as a standardized way for computers to communicate across a network From the DARPA experiment came the understanding that networking would become increasingly common – and increasingly complex The OSI model was developed, based on the DARPA model, and approved by OSI subcommittee of the International Organization for Standardization (ISO) The OSI model defined seven layers for standard, reliable network commu-nications: physical, data link, network, transport, session, presentation, and application The acronym commonly used to remember this is (in reverse

order): All People Seem To Need Data Processing The OSI model was

cov-ered in depth in Chapter 5 It will, however, continue to be used through the rest of the text As you can see, the use of it becomes very important when discussing network protocols, the heart of this chapter’s content For the Network exam, make certain that you memorize the OSI model and the placement of TCP/IP within it

The TCP/IP suite provides the functionality specified in the OSI model using the four related layers of the DoD model: network interface, inter-net, host-to-host, and application This is because it’s hard to map TCP/

IP to the OSI model, also discussed in the previous chapter The network

Exam warning

NAT hides the local internal IP addresses from external Internet users, which provides a layer of security to your network.

interface maps to the physical and data link layers; the Internet Layer maps

to the OSI’s network layer; the host-to-host layer maps to the transport

layer; and DoD’s application layer maps to the session, presentation, and

application layers of the OSI model Some of the more commonly known

application layer protocols are FTP, HTTP, POP3, WINS, DNS, and DHCP

Within these layers are protocols that are covered in this chapter, all of which

you must remember for the exam

At the Internet layer is the IP used for addressing data for delivery across

a network Understanding IP addressing is a fundamental skill needed both

on the job and for this exam IP addresses are 32-bit addresses represented

in dotted decimal format (w.x.y.z) The 32 bits contain both a network and

host ID To understand IP addressing, you must first understand how to

convert the dotted decimal numbers into binary and back to decimal To

send data to the correct location, the IP address in the packet is compared,

using bitwise ANDing, to the subnet mask If the result is the local network

address, the packet stays on the local network If ANDing indicates that the

network address is external to the local network, the packet is sent to the

defined default gateway for forwarding

Network addresses were originally designed in a class-based system

Class A networks use the first octet (w) and have an address range of 1.x.y.z

to 126.x.y.z Class B networks use the first two octets for the network ID and

have an address range of 128.0.y.z to 191.255.y.z Class C networks use the

first three octets for the network ID and have an address range of 192.0.0.z

to 223.255.255.z Each class of network, when undivided, uses a default

sub-net mask, which identifies which bits of the IP address represent the sub-network

ID The default subnet masks are: Class A, 255.0.0.0; Class B, 255.255.0.0;

Class C, 255.255.255.0

Classful networks can be subdivided for greater efficiency by reducing

the number of hosts per segment, thus reducing network traffic

Sub-netting requires the subdividing of the class-based network IDs using

custom subnet masks These are developed by using bits from the host

address space The number of subnets that can be created from the

net-work ID depends on the number of bits taken from the host address

space There is an inverse relationship between the number of subnets

and the number of hosts per subnet Typically, organizations choose to

have a maximum of 256 devices per subnet for the most efficient use of

network bandwidth

Packets destined for networks that are not local are forwarded using

gateways or routers IP routing involves resolving the hostname or

NetBIOS name to an IP address and resolving the IP address to a MAC address

NetBIOS name resolution uses four different node types to resolve names to

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IP addresses: broadcast (B-node), peer-to-peer (P-node), mixed (M-node), and hybrid (H-node) Names can also be resolved by using a host file or through the DNS Names must be resolved to IP addresses The Address Resolution Protocol (ARP) is used to resolve the IP address to the Media Access Control (MAC) address that is unique to each NIC manufactured

Routing on a network can be static or dynamic, depending on whether

or not Dynamic Routing Protocols are installed Many computers designed

as routers include this function, but a Windows Server 2003 computer can be set up as a router by installing two NICs, enabling the Routing and Remote Access Service (RRAS) via the registry and installing and config-uring both the RIP and OSPF Dynamic Routing Protocols Four com-monly used routing utilities are route, ping, tracert, and pathping Each can

be run from the command line in Windows Protocols such as APIPA and DHCP help to get systems logically addressed dynamically Protocols such as DNS and WINS help to provide name resolution as well

In this chapter, we also covered the use of protocol ports and the impor-tance of them You must memorize these port assignments for the Network exam You will definitely not only see them there, but also need to use them daily on the job as a Network certified technician

Understanding the details of the TCP/IP suite is fundamental to manag-ing computers in today’s networked environment as well as to passmanag-ing the Nework exam

ExAM oBJECTIvES FAST TrACK

TCp/Ip

The TCP/IP stack does not map neatly to the OSI model, as the

■

■ OSI model was developed after TCP/IP

In the following table, Class A, B, and C addresses are listed for

■

■ quick recall It’s imperative for the Network exam to have the following information memorized

The primary role of IP is to provide logical addresses and support

■

■ the routing of traffic to its destination

IPv4 addresses are 32-bit addresses expressed in dotted decimal

■

■

notation of four octets, w.x.y.z.

Packets are sent with a destination name or IP address included in

■

■

the packet headers

Ipv6

IPv6 addresses are 128-bit addresses expressed as AAAA:AAAA:

■

■

AAAA:AAAA:AAAA:AAAA:AAAA:AAAA

IPv6 addresses are 128-bit identifiers for interfaces and sets of

■

■

interfaces, not nodes

Three general types of addresses exist within IPv6: unicast, anycast,

■

■

and multicast

understanding Ip Addressing

IP addresses contain the network address space followed by the host

■

■

address space

Originally, IP addresses were assigned four classes: A, B, C, and D

■

■

Class E is considered experimental and is not supported in

Windows Server 2003

Remember that 127.0.0.0 is reserved for loopback addresses

■

■

Dotted decimal notation can be converted to its binary equivalent

■

■

by using weighted binary bits notated with 2n where n is the

num-ber of bits

Public IP addresses are IP addresses that fall in a range other than

■

■

those designated as private Public IP addressing is addressing

assigned to you for use on the public Internet Two such

organiza-tions were created to manage the use of such addressing: IANA and

the ICANN

understanding Subnetting

The default subnet masks for Class A, B, C, and D are, respectively,

■

■

255.0.0.0, 255.255.0.0, 255.255.255.0, and 255.255.255.255

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Custom subnet masks (also called variable length subnet masks)

■

■ are used when a network is divided, by using bits from the host address space that are added to the network address space

A logical bitwise AND comparison is used to compare the bits of

■

■ the IP address to the subnet mask The result of the comparison is the network ID

Default subnet masks are defined for undivided Class A, B, C, and

■

■

D networks

Strategies to Conserve Addresses

The growth of networking required a new solution CIDR was

■

■ implemented as a classless addressing schema

CIDR reduces route table sizes as well as IP address waste Instead

■

■

of full Class A, B, or C addresses, organizations can be allocated subnet blocks

VLSMs conserve IP addresses by tailoring the mask to each subnet

■

■ Subnet masks are appropriated to meet the amount of addresses required

rFC 1918 – private Network Addresses

RFC1918 conserves globally unique IP addresses by providing three

■

■ blocks of addresses that are never officially allocated to any organi-zation Those address ranges are as follows:

Static IP addressing is done manually It is hard to manage and

■

■ adjust, as you have to visit every system that has an address if you want to change the addressing scheme from one range of IP addresses to another, such as from 192.168.1.0 to 10.1.1.0

Address Block Classful Equivalent length prefix Number of Addresses

10.0.0.0–10.255.255.255 1 Class A

256 Class B 65,536 Class C

172.16.0.0–172.31.255.255 16 Class B

192.168.0.0–192.168.255.255 1 Class B

Dynamic IP addressing is done automatically This can be done

■

■

with DHCP or with APIPA

Self-assigned (APIPA [Automatic Private Internet Protocol

Address-■

■

ing]) is a Microsoft Windows-based service (but available to any OS)

that will allow for a Windows 98, ME, 2000, 2003, or XP system

to assign itself an address from a designated private block

rang-ing from 169.254.0.1 to 169.254.255.254, with a subnet mask of

255.255.0.0

Name resolution occurs using WINS or an lmhosts file (for

Net-■

■

BIOS names) or DNS or a hosts file (for hostnames)

Multicast, Broadcast, and unicast

Multicasting benefits are not limited to video/audio needs Multicast

■

■

can be used to push updates to multiple hosts simultaneously, thus

reducing the effort and time involved in doing one update at a time

Multicast addresses cannot be used as source addresses for any traffic

■

■

Multicast addresses are not

■

■ assigned to a device; rather, a device

proceeds to listen for and receive traffic destined to a multicast

group that it has joined by some process

Unicast is the transmission of data from one host to another, one

■

■

host at a time

Broadcasts can consume a significant amount of bandwidth;

con-■

■

nections are based on a one-to-all method transmission

understanding Basic Ip routing

MAC addresses are 16-byte addresses expressed as

■

■

AA:AA:AA:AA:AA:AA

Routers can use static or dynamic routing Static routing requires

■

■

new entries to be entered manually Dynamic routing updates route

information automatically

Dynamic routing means that a protocol like RIP or OSPF is used to

■

■

handle the routing instead of you statically have to configure each

routers RIT

Link State Routing Protocols include OSPF and IS-IS

■

■

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Distance Vector Routing Protocols include RIP, RIPv2, and BGP

■

■ Hybrid Routing Protocols include the Cisco proprietary EIGRP

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■ IGP or Interior Gateway Protocols are designed for routing use

■

■ inside of a LAN

Static routing is administered by the network technician and does

■

■ not change

Dynamic routing is able to change as conditions warrant it This

■

■ requires the use of a routing protocol

Convergence is the state when all routers are making decisions

■

■ based on the same network information

IP address to MAC address resolution occurs through ARP request

■

■ and reply messages The reverse, MAC to IP resolution, uses RARP requests and replies

ExAM oBJECTIvES FrEquENTly ASKEd quESTIoNS

I’m still a bit rusty with binary, dotted decimal, conversions, and so Q:

forth Can’t I use a program to do all this for me when I’m working

on my corporate network?

Yes, there are programs available that will do all the conversions A:

and subnet calculations you need However, those won’t be avail-able on the exam and they may not always be availavail-able to you on the job Keep working through the conversions and examples in this chapter until you feel confident of your understanding and application of the material

Will I be given a table of Class A, B, and C networks, subnets and Q:

subnet masks for the exam?

No, you will not You’ll need to memorize the definitions of Class A:

A, B, and C networks, along with their associated default subnet masks You will not need to calculate complex subnet masks for the Network exam, but you will need to understand the concepts behind

it, as well as logical addressing of network protocols in general

Will I be expected to know about private addressing for the Q:

Network exam?

Yes, you will You need to master the ranges listed They are A:

10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and

192.168.0.0 to 192.168.255.255 You will be expected to know

these, not only for the exam, but also on the job

Will I need to know how to configure an e-mail server for this

Q:

exam? With all this talk about e-mail protocols such as SMTP,

what do I need to focus my studies on?

No, you will not need to know how to configure anything for the

A:

exam The exam is more straightforward, asking you very simple

paths to get to places in Windows that are very common Other

than that, all other questioning is pretty straightforward

SElF TEST

You are a network administrator and you have 1,000 client

1

computer that you need to set up with IP addressing What protocol

would you use to set up these client computers with an IP address,

subnet mask, default gateway, and preferred DNS server?

A DHCP

B APIPA

C BOOTP

D TFTP

You have been given an IP address in binary form The address

2

you have been given is 11000000.00000000.00000000.00000001

What is this IP address in decimal form?

A 127.0.0.1

B 191.0.0.1

C 137.0.0.1

D 192.0.0.1

You have been asked by your colleague Bobbi about classfull

3

IP addresses Which of the following is NOT a normal IP address

class?

A CLASS A

B CLASS D

C CLASS F

D CLASS C

ChApTEr 7: TCP/IP and Routing

354

You have been asked to explain what a certain IP address is

4

used for The IP address is 224.0.0.1 What are addresses in the 224.0.0.0 range used for?

A SNMP

B HTTP

C POP3

D Multicasting You are having a conversation with another networking

profes-5

sional and the subject of protocols comes up You are asked which

of the following are IGP routing protocols?

A OSPF

B BGP

C IS-IS

D RIP You have been asked to lay out a new small office network Which

6

of the following IP address ranges could you use because they are Private address ranges?

A 11.0.0.0 to 11.255.255.255.255

B 137.1.0.0 to 137.1.255.255

C 191.4.0.0 to 191.4.255.255

D 192.168.5.0 to 192.168.5.255 You have a user who cannot get connected to the Internet You

7

have the user run IPCONFIG/ALL and he reads you the IP address

of 169.254.1.3 What is wrong with this system?

A System has a static IP address

B System has an APIPA address

C System has a bad address

D System has a classless address

A user has been given an IP address of 192.168.1.1 with a subnet

8

mask of 255.255.255.0 How would you express the subnet mask for this address using CIDR notation?

A /24

B /8

C /16

D /22

A user has been given an address of fe80::9c5f:9695:f235:0051

9

What kind of address has she been given?

A IPv4 address

B IPv6 address

C MAC address

D GUID

You have a network with several thousand users You do not want

10

to manually configure every user’s computer What protocol would

you use to automatically configure their IP addresses?

A SNMP

B APIPA

C DHCP

D TFTP

You have been asked to implement routing on a simple

corpo-11

rate local area network All connections will be the same speed

Which routing protocol would you use for a simple network like

this?

A OSPF

B RIP

C BGP

D IS-IS

You have been asked to connect routing for your corporate network

12

to your ISP Which routing protocol would you use for an exterior

connection?

A OSPF

B RIP

C BGP

D EIGRP

You have a main corporate location and several branch locations

13

All locations access the Internet through corporate What type of

routing would you enable for this approach?

A None

B Dynamic

C Static

D Classless