internet protocol suite and all its interface

8/10/2019 internet protocol suite and all its interface

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1

-IPv4AddressingandSubnetting-

Har d wa re Ad d r e ssin g

A hardwareaddressis used to uniquely identify a host

withina local network. Hardware addressing is a functionof the Data-Linklayer of the OSI model (Layer-!.

"thernet utili#es the $%-&it MACaddressas its hardwareaddress. 'he A) address is often hardcoded on *hysicalnetwork interfaces+ though some interfaces su**ortchanging the A) address using s*ecial utilities. In,irtuali#ation en,ironments+ dynamically assigning A)addresses is ,ery common.

A A) address is most often re*resented in hexadecimal,using one of two acce*ted formats

$/A0/1/

$/.A0./1/

'he first si2 he2adecimal digits of a A) address identify themanufacturerof the *hysical network interface. 'his is

referred to as the OI!Organi"ati#nalni$ueIdenti%ier&''he last si2 digits uniquely identify the host itself+ and arereferred to as the h#stID.

'he A) address has one shortcoming 3 it contains nohierarchy.A) addresses *ro,ide no mechanism to createb#undaries&etween networks. 'here is no method todistinguish one network from another.

'his lack of hierarchy *oses significantdi4iculties to networkscala&ility. If onlyLayer- hardware addressing e2isted+ all

hosts would technically e2ist on the samenetwork.Internetworks like the Internet could not e2ist+ as it would &eim*ossi&le to se*arate mynetwork from yournetwork.

Imagine if the entire Internet e2isted *urely as a singleLayer- switched network. Switches+ as a rule+ will forwarda &roadcast out every*ort. 5ith &illions of hosts on theInternet+ the resulting &roadcast storms would &ede,astating. 'he Internet would sim*ly colla*se.


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'he scala&ility limitations of Layer- hardware addressesare mitigated using l#gicaladdresses,co,ered ingreat detail in this guide.

Logic a l A dd r e ssing

Logical addressing is a function of the (etw#rklayer ofthe OSI odel (Layer-/!+ and *ro,ides a hierarchicalstructure to se*arate networks. Logical addresses arene,er hardcoded on *hysical network interfaces+ and can&e dynamically assigned and changed freely.

A logical address contains two com*onents

6 (etw#rkID3 identifies which network a host&elongs to. 6 )#stID3 uniquely identifies thehost on that network.

"2am*les of logical addressing *rotocols includeInternetw#rkPacket*xchange!IP+&and InternetPr#t#c#l!IP&. I78 was *redominantly used on 9o,ellnetworks+ &ut is now almost entirely de*recated. IPis themost widely-used logical address+ and is the &ack&one*rotocol of the Internet.

I nte r n e t P r ot o co l ( I P)

In the 1:;


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data accordingly.

I7 was originally de?ned in @) ;+ and has &een re,isedse,eral times. I7 Bersion $ (IPv4! was the ?rst ,ersion toe2*erience wides*read de*loyment+ and is de?ned in @);:1. I7,$ will &e the focus of this guide.

I7,$ em*loys a 01-bitaddress+ which limits the num&er of*ossi&le addresses to $+:$+:;+:. I7,$ will e,entually &ere*laced &y I7 Bersion (IPv2!+ due to a shortage ofa,aila&le I7,$ addresses. I7, is co,ered in great detail inanother guide.


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I Pv4 Ad dr es sin g

A core function of I7 is to *ro,ide logical addressing forhosts. An IPaddress*ro,ides a hierarchical structure to&oth uniquely identify a host+ and what networkthat hoste2ists on.

An I7 address is most often re*resented in decimal,in thefollowing format

1C%.%.1$./

An I7 address is com*rised of four #ctets,se*arated &y *eriods

irstOctet

1C%

SecondOctet

%

'hirdOctet

1$

ourth Octet

/

"ach octet is an 3-bitnum&er+ resulting in a 01-bitIPaddress. 'he smallest *ossi&le ,alue of an octet is 0,or00000000in &inary. 'he largest *ossi&le ,alue of an octet is255+ or 11111111in &inary.

'he a&o,e I7 address re*resented in &inary would look as follows

irstOctet

11111

SecondOctet

11

'hirdOctet

111

ourth Octet

11

Dec im al to B in a r y C o nv e r s io n

'he sim*lest method of con,erting &etween decimaland &inary is to remem&er the following ta&le

1% $ / 1 % $ 1

'o con,ert a decimal num&er of 172to &inary+ start with theleftmost column. Since 172is greater than 128+ that &inary&it will &e set to 1. 9e2t+ add the ,alue of the ne2t column(128+6!1"2#. Since 172is less than 1"2,that &inary&it will &e set to 0.

Again+ add the ,alue of the ne2t column (128+$2!160#.Since 172is greater than 160+ that &inary &it will &e set to


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1.)ontinue this *rocess until the columns with &inary &itsset to 1add u* to 1;

=ecimal 1% $ / 1 % $ 1 0inary 1 1 1 1


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B i n a r y t o De c im al C o nv e r s io n

)on,erting from &inary &ack to decimal is e,en sim*ler.A**ly the &inary num&er to the con,ersion ta&le+ and thenadd u* any columns with &inary &its set to 1.

or e2am*le+ consider the &inary num&er of 11110001%=ecimal 1% $ / 1 % $

1 0inary 1 1 1 1 1

0y adding 128+6+$2+16+1,it can &e determinedthat 11110001equals 21.

The S ! n e t "a s #

7art of an I7 address identifies the network.'he other *artof the address identifies the host.A subnetmaskis

required to *ro,ide this distinction

1C%.%.1$./ CC.CC..

'he a&o,e I7 address has a su&net mask of 255.255.0.0.'he su&net mask follows two rules

6 If a &inary &it is set to a 5(or on! in a su&net mask+ the

corres*onding &it in the address identifies thenetw#rk.

6 If a &inary &it is set to a 6(or off! in a su&net mask+ thecorres*onding &it in the address identifies the h#st.

Looking at the a&o,e address and su&net mask in &inary

I7 AddressSu&netask

11111.11.111.1111111111.11111111..

'he first 1 &its of the su&net mask are set to 1. 'hus+ thefirst 1 &its of the address (158.80! identify the network. 'helast 1 &its of the su&net mask are set to 0. 'hus+ the last 1&its of the address (16.$! identify the unique hoston thatnetwork.

'he network *ortion of the su&net mask must &ec#ntigu#us. or e2am*le+ a su&net mask of 255.0.0.255is


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not ,alid.


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The S ! n e t "a s # ( c o ntin e d)

Hosts on the same logical network will ha,e i&enticalnetwork addresses+ and can communicate freely. ore2am*le+ the following two hosts are on the samenetwork

Host A 1C%.%.1$.1CC.CC.. Host 0

1C%.%.1$.11CC.CC..

0oth share the same network address (158.80!+ which isdetermined &y the 255.255.0.0su&net mask. Hosts thatare on &ifferentnetworks cannot communicate without anintermediating de,ice. or e2am*le

Host A 1C%.%.1$.1CC.CC.. Host 0

1C%.%C.1$.11CC.CC..

'he su&net mask has remained the same+ &ut the networkaddresses are now different (158.80and 158.85res*ecti,ely!. 'hus+ the two hosts are noton the samenetwork+ and cannot communicate without a r#uter&etween them. /#utingis the *rocess of forwarding *acketsfrom one network to another.

)onsider the following+ trickier e2am*le

Host A 1C%.%.1.1CC.$%.. Host 0

1C%.;:.1.1CC.$%..

'he s*eci?ed su&net mask is now 255.28.0.0+ which doesn


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@emem&er+ the 5(or #n&&its in the su&net mask identify thenetwork*ortion of the address. In this e2am*le+ the first 1$bits(the % &its of the ?rst octet+ and the first C &its of thesecond octet! identify the network. Looking at only the first1/ &its of each address

Host A

AddressHost 0Address

11111.1

111111.11

)learly+ the network addresses are notidentical. 'hus+ thesetwo hosts are on se*arate networks+ and require a router tocommunicate.


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I P A d d r es s Cla s s e s

'he I7,$ address s*ace has &een structured into se,eralclasses. 'he ,alue of the %irst#ctetof an addressdetermines the class of the network

Class $irst %ctet&ange

)lass A 1 - 1;)lass 01% - 1:1 )lass )1: - / )lass =$ - /:

De'altS!net"as#CC...

CC.CC..

CC.CC.CC. -

ClassAnetworks range from 5to 517''he &efaultsu&netmask is CC.... 'hus+ &y &efault,the first octet defines the

network+ and the last three octets define the host. 'hisresults in a ma2imum of 517)lass A networks+ with52,777,154hosts *er networkD

"2am*le of a )lass Aaddress

AddressSu&netask

$./.C$.1CC...

Class8networks range from 513to 595. 'he &efaultsu&netmask is CC.CC... 'hus+ &y &efault,the ?rst two octetsdefine the network+ and the last two octets define the host.

'his results in a ma2imum of 52,034)lass 0 networks+ with2:,:04hosts *er network.

"2am*le of a )lass 0address

AddressSu&netask

1C.$1.1.1:C

CC.CC..

ClassCnetworks range from 591to 110''he &efaultsu&net mask is CC.CC.CC.. 'hus+ &y &efault,the firstthree octets define the network+ and the last octet de?nesthe host. 'his results in a ma2imum of 1,697,5:1)lass )networks+ with 1:4hosts *er network.


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"2am*le of a )lass )address

AddressSu&netask

;.;:.//.CC.CC.CC.

ClassDnetworks are reser,ed for multicasttra4ic. )lass= addresses do not use a su&net mask.


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C I D& (Cla ssle s s Int e rD o m a in & o ting)

ClasslessInter-D#main/#uting!CID/&is a sim*lifiedmethod of re*resenting a su&net mask. )I=@ identifies thenum&er of &inary &its set to a 5(or on! in a su&net mask+*receded &y a slash.

or e2am*le+ a su&net mask of 255.255.255.20would &ere*resented as follows in &inary

11111111.11111111.11111111.1111

'he first % &its of the a&o,e su&net mask are set to 1. 'he)I=@ notation for this su&net mask would thus &e*+.

'he )I=@ mask is often a**ended to the I7 address. ore2am*le+ an I7 address of 1"2.168.1.1and a su&net

mask of 255.255.255.0would &e re*resented as followsusing )I=@ notation

1:.1%.1.1 E$

Add r e ss C las s e s v s , S ! n e t "a s #

@emem&er the following three rules6 'he %irst#cteton an address dictates the classof thataddress.

6 'he subnetmaskdetermines what *art of anaddress identifies the network+ and what *artidentifies the host.

6 "ach class has a de'altsu&net mask. A networkusing its default su&net mask is referred to as aclass%ulnetw#rk.

or e2am*le+ 10.1.1.1is a )lass A address+ and its defaultsu&net mask is 255.0.0.0('8in )I=@!.

It is entirely *ossi&le to use su&net masks otherthanthe default. or e2am*le+ a )lass 0 su&net mask can&e a**lied to a )lass A address

1.1.1.1 E1

Howe,er+ thisd#esn#tchangetheclass#%theab#veaddress. It remains a )lass A a&&ress+ which has &eensu&netted using a )lass 0 mask.

@emem&er+ the onlything that determines the class of an


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I7 address is the first octet of that address. Likewise+ thesu&net mask is the onlything that determines what *artof an address identi?es the network+ and what *artidentifies the host.


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S ! n e t a n d B ro a d c ast Ad d r e s s es

On eachI7 network+ two host addresses are reser,edfor s*ecial use 6 'he subnet(or netw#rk!address6 'he br#adcastaddress

(eitherof these addresses can &e assigned to an actual host.

'he subnetaddress is used to identify thenetw#rkitsel%. A routing ta&le contains a list of known networks+and each network is identified &y its su&net address.Su&net addresses contain all6bitsintheh#st.#rti#nof the address.

or e2am*le+ 1"2.168.1.0'2is a su&net address. 'his can&e determined &y looking at the address and su&net maskin &inary

I7 AddressSu&netask

11.111.1.11111111.11111111.11111111.

9ote that all host &its in the address are set to 0.

'he br#adcastaddress identifies allhosts on a *articular

network. A *acket sent to the &roadcast address will &erecei,ed and *rocessed &y e,ery host on that network.0roadcast addresses contain all5bitsintheh#st.#rti#nof the address.

or e2am*le+ 1"2.168.1.255'2is a &roadcast address. 9otethat all host &its are set to 1%

I7 AddressSu&netask

11.111.1.1111111111111111.11111111.11111111.

0roadcasts are one of three ty*es of I7 *ackets6 nicastsare *ackets sent from one host to one other host6 Multicastsare *ackets sent from one host to a groupofhosts6 8r#adcastsare *ackets sent from one host to all

other hosts on the local network


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A router+ &y default+ will never%#rwarda multicast or&roadcast *acket from one interface to another.

A switch+ &y default+ will forward a multicast or &roadcast*acket #utever;.#rt+ e2ce*t for the *ort that originatedthe multicast or &roadcast.


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:

S ! n e t tin g

Subnettingis the *rocess of creating new networks (orsubnets#&y stealingbitsfrom the host *ortion of a su&netmask. 'here is one ca,eat stealing &its from hosts creates

m#renetworks &ut %ewerhosts *er network.

)onsider the following )lass ) network

1:.1%.C$.

'he default su&net mask for this network isCC.CC.CC.. 'his single network can &e segmented+ orsubnette&+ into multi*le networks. or e2am*le+ assume aminimum of 10new networks are required. @esol,ing thisis *ossi&le using the following magical formula

n

'he e2*onent Fn


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1.

S ! n e t tin g ( c o n tin e d)

In the *re,ious e2am*le+ a )lass ) network was su&nettedto create 16new networks+ using a su&net mask of255.255.255.20(or '28in )I=@!. our &its were stolen in

the su&net mask+ lea,ing only four &its for hosts.

'o determine the num&er of hosts this results in+ foreach of the new 1 networks+ a slightly modified formulais required

n3

)onsider the result if four &its are a,aila&le for hosts

n3

$3 1 3 54usableh#sts.er

netw#rk'hus+ su&netting a )lass ) network with a E% maskcreates 1 new networks+ with 1$ usa&le hosts *ernetwork.

5hy is the formula for calculating usa&le hosts n3

0ecause it is never.#ssibleto assign a host an addresswith all 0or all 1&its in the host*ortion of the address'

'hese are reser,ed for the su&net and &roadcast addresses+res*ecti,ely. 'hus+ e,ery time a network is su&netted+usea&le host addresses are lost.

The*n

*&leandS!netted-etwor#s

'o a,oid confusion+ it was historically unacce*ta&le to usethe ?rst and last new networkscreated when su&netting+ asit is *ossi&le for a classful network to ha,e the same su&netand &roadcast address as its su&netted networks. 'his

required the n3 formula to also &e used when calculating

the num&er of new networkscreated while su&netting.Howe,er+ this is n#l#ngerarestricti#nfor modernequi*ment and routing *rotocols. S*ecifically+ on )isco IOSde,ices+ the following command is now ena&led &y default

/#uter!c#n%ig&= ipsubnet)*ero

'he ipsubnet)*erocommands allows for the use of networkswith all .or all /bitsin the stolennetwork *ortion of theaddress. 'hus+ the formula for calculating the num&er of new


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networks created is sim*ly 1n.

@emem&er though+ the formula for calculating usa&le hostsis

alwa;s1n

>1.


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11

Det e r m in in g t he & a nge o' S ! n e t t e d -e t w o r # s

=etermining the rangeof the newly created networks can&e accom*lished using se,eral methods. 'he longmethodin,ol,es some &inary magic.

)onsider the e2am*le 1"2.168.25.0network again+ whichwas su&netted using a 255.255.255.20mask

1:.1%.C$.CC.CC.CC.$

11.111.1111111.11111111.11111111.11111111.1111

Su&netting stole four &its in the fourth octet+ creating a totalof 16new networks. Looking at onlythe fourth octet+ the first

newly created network is 0000. 'he second new network is0001. )alculating all *ossi&le *ermutations of the four stolen&its

Binary Decimal Binary Decimal Binary Decimal . . .11 .: .11 .1:.1 .1 .111 .11 .111 .%.1 ./ .1 .1% .111 .$.11 .$% .11 .1$$ .1111 .$.1 .$ .11 .1.11 .% .111 .1;

9ote that this equates to e2actly 16new networks. 'hedecimal ,alue re*resents the first (or the subnet! address ofeach newly created network. 'o determine the range for thehosts of the firstnew network

Binary Decimal Binary Decimal Binary Decimal . . . . . .1. .1 . .; . .1/

. . . .% . .1$

. ./ . .: . .1C

. .$ . .1

. .C . .11

'he &inary ,alue has &een s*lit to em*hasi#e the se*arationof the stolen network&its from the host&its. 'he ?rstaddress has all 0&its in the host *ortion (0000!+ and is thesubnetaddressfor this network. 'he last address has all 1


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&its in the host *ortion+ and thus is the br#adcastaddressfor this network. 9ote that there are e2actly 54usableaddressesto assign to hosts.


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1

Det e r m in in g t he & a nge o' S ! n e t t e d -e t w o r # s (c o n t i n e d)

)alculating the ranges of su&netted networks can quickly&ecome tedious when using the long &inary method. 'heshortcutmethod in,ol,es taking the su&net mask

(255.255.255.20from the *re,ious e2am*le!+ andsu&tracting the su&netted octet (20! from 256.

C 3 $ 1

Assuming ipsubnet)*erois ena&led+ the first network will&egin at 0.'hen+ sim*ly continue adding 16to identify thefirst address of each new network

1 / $% $ % : 11 1% 1$$ 1 1; 1: %$ $

Jnowing the firstaddress of each new network makes itsim*le to determine the lastaddress of each network

irsta&&ressofnetwork

-asta&&ressofnetwork

1 / $%$

1C /1 $; /;:

% : 11 1% 1$$

:C 111 1; 1$/1C:

Only the ?rst 1 networks were calculated+ for &re,ity. 'hefirst address of each network &ecomes the subnetaddressfor that network''he last address of each network &ecomesthe br#adcastaddressfor that network'

Once the first and last address of each network is known+determining the usa&le range for hosts is straightforward

ubneta&&ress

1

1 / $%$

1; // $:C

% : 11 1% 1$$

%1 :; 11/ 1: 1$C

/sableange

1$ / $ ;%

roa&casta&&ress 1C /1 $; /;:

:$ 11 1 1$1C%

:C 111 1; 1$/1C:


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Hosts on the same network (such as 1"2.168.25.2and1"2.168.25.1! can communicate freely.

Hosts on di4erent networks (such as 1"2.168.25.61and1"2.168.25.66! require a router to communicate.


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1/

C l a s s A S ! n e t ting 0 1 a m2le

)onsider the following su&netted )lass A network 1...CC.CC.$%.

9ow consider the following questions6 How many new networks were created6 How many usa&le hosts are there *er network6 5hat is the full range of the ?rst three networks

0y default+ the 10.0.0.0network has a su&net mask of255.0.0.0. 'o determine the num&er of &its stolen

CC...CC.CC.$%.

11111111...11111111.11111111.11111.

)learly+ 50bitsha,e &een stolen to create the new su&netmask. 'o calculate the total num&er of new networks

n

1/

3591newnetw#rkscreated

'here are clearly 55bitsremaining in the host *ortion of the mask

n3

113 $% 3 1642usableh#sts.er

netw#rk)alculating the ranges is a &it tricky. Gsing the shortcutmethod+ su&tract the third octet (28#of the su&net mask(255.255.28.0! from 256.

C 3 $% %

'he first network will &egin at 0+ again. )#wever+ the rangesare s*read across multi*le octets. 'he ranges of the firstthree networks look as follows

ubneta&&ress

1...

1...1

1..%.

1..%.1

1..1.

1..1.1

/sableange


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su**orts a ,ast address s*ace.

0oth 9A' and I7, are co,ered e2tensi,ely in other guides.


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1C

&e s e r v e d I P v 4 A dd r e s s e s

In addition to the three *ri,ate I7,$ ranges+ se,eralother addresses and ranges are reser,ed for s*ecific*ur*oses

6 'he 6'6'6'66network is used to identify allnetw#rks,and is referred to as the de%aultr#ute'If adefault route e2ists in a routing ta&le+ it will &e usedonly if there is nota more specicroute to a *articulardestination. @outing and default routes are co,erede2tensi,ely in another guide.

6 'he 6'6'6'63range is used to identify hosts on thelocalnetwork. Addresses in this range can only &e used

as a sourceaddress. 'he most commonly used addressin this range is 6'6'6'601,which a host will use whendynamically attem*ting to learn its I7 address ,ia=ynamic Host )on?guration 7rotocol (=H)7!. =H)7 isco,ered e2tensi,ely in another guide.

6 'he entire 517'x'x'x3range is reser,ed fordiagnostic *ur*oses. 'he most commonly used addressin this range is 517'6'6'5+ which identifies the local

host+ and is referred to as the l##.backor l#calh#staddress.

6 'he 529'1:4'x'x52range is reser,ed for Automatic7ri,ate I7 Addressing (A7I7A!. A host assigns itself anaddress in this range+ if it cannot dynamically o&tainan address from a =H)7 ser,er.

6 'he 114'x'x'x>109'x'x'xranges are reser,ed formulticast+ and are referred to as ClassDaddresses.

6 'he 146'x'x'x>1::'x'x'xranges are reser,ed forfuture and e2*erimental use+ and were formerlyreferred to as Class*addresses.

6 'he 1::'1::'1::'1::address can &e used as a&roadcast address for the local network.


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1A

The IPv4 H ea d e r

'he I7,$ header is com*rised of 51re$uired%ieldsand 5#.ti#nal%ield''he minimum length of the header is 526bits!16b;tes&'

iel& -ength 3escription

Bersion $ &its 4ersionofinthiscase,v#Internet Header $ &its pecifiesthelengthofthehea&er

=S)7 % &its lassifiestrafficfor9o'otal Length 1 &its pecifiesthelengthofboththehea&eran&Identification 1 &its /ni:uelyi&entifiesfragmentsofapacket

lags / &its lagsforfragmentationragment O4set 1/ &its &entiesthefragmentrelativetothestart

'ime to Li,e % &its 3ecremente&byeachroutertraverse&7rotocol % &its pecifiesthenetupperlayerprotocol

Header 1 &its hecksumforerrorcheckingSource Address / &its ourceva&&ress

=estination / &its 3estinationva&&ressO*tions Baria&le ;ptionalel&forvariousparameters

'he $-&it ?ersi#n%ieldis set to a ,alue of for I7,$.

'he $-&it Internet)eaderLength@eldidenti?es the

length of the I7,$ header+ measured in /-&it wor&s. 'heminimum of length of an I7,$ header is 1 &its+ or C words(/ 2 C 1!.

'he %-&it Di%%erentiatedServiceC#deP#int!DSCP&%ieldis used to classify traf?c for Kuality of Ser,ice (KoS!*ur*oses. KoS is co,ered in great detail in other guides. 'hisfield was *re,iously referred to as the 'y*e of Ser,ice ('oS!field.

'he 1-&it #talLength@eldidenti?es the total *acketsi#e+ measured in bytes,including &oth the I7,$ headerand the data *ayload. 'he minimum si#e of an I7,$ *acketis &ytes 3 essentially a header with no *ayload. 'hema2imum *acket si#e is 2:,:0:b;tes.


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1;

The IPv4 H ea d e r (con tin e d)

iel& -ength 3escription

Bersion $ &its 4ersionofinthiscase,v#

Internet Header $ &its pecifiesthelengthofthehea&er=S)7 % &its lassifiestrafficfor9o

'otal Length 1 &its pecifiesthelengthofboththehea&eran&Identification 1 &its /ni:uelyi&entifiesfragmentsofapacket

lags / &its lagsforfragmentationragment O4set 1/ &its &entiesthefragmentrelativetothestart

'ime to Li,e % &its -imitsthelifetimeofapacket7rotocol % &its pecifiesthenetupperlayerprotocol

Header 1 &its hecksumforerrorchecking

Source Address / &its ourceva&&ress=estination / &its 3estinationva&&ressO*tions Baria&le ;ptionalel&forvariousparameters

An I7,$ *acket that is larger than the Maximumransmissi#nnit!M&si#e of a link must &e%ragmented. 0y default+ the 'G for "thernet is 5:66b;tes'

'hree fields are used when a *acket must &e fragmented -

the 1-&it Identi@cati#n@eld+ the /-&it lags%ield+ andthe 1/-&it ragmentOBset%ield. "ach fragment of the*acket is marked with the same &enticationnum&er. 'heragment;ffsetallows the destination host to reassem&lethe fragments in the *ro*er order.

'he lagsfield dictates two conditions

6 D#n


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1:

I Pv4 Pr o t o co l - m !e r s

'he %-&it Pr#t#c#l@elds*ecifies the ne2t u**er-layerheader within the data *ayload of the *acket. 'hese u**er-layer *rotocols are identi?ed using IPPr#t#c#l(umbers.

'he following is a list of common I7 7rotocol 9um&ers+ asassigned &y the IA9A

Pr#t#c#l(umber

1

:1;$$;C

C1%%%:

..er-La;erPr#t#c#l

I)7I7')7

I@7G=7@SB7@"

I7S")"S7

I7S") AH"I@7OS7

In I7,+ this field is referred to as the (ext)eader%ield'


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6 Host0 res*onds to the A@7 request with an A@7 re*lycontaining its A) address (AAAA.0000.))))!.@outerA can now construct a Layer- frame+ with adestination of Host0


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re*lies. )ached entries will e,entually &e aged out of theA@7 ta&le. 'he aging time will ,ary de*ending on theo*erating system+ and can range from se,eral seconds tose,eral hours.


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/

Tr o ! les ho o tin g I P sing IC"P

'he InternetC#ntr#lMessagePr#t#c#l!ICMP&is usedfor a multitude of informational and error messaging*ur*oses.

'he following is a list of common I)7 ty*es and codes

=ype

o&e66

0 -

1/$;:1

3escription*ch#/e.l;

Destinati#nnreachable(etwork

/nreachable>ost/nreachablerotocol/nreachableort/nreachableragmentation(ee&e&?3on@tragmentlaget3estination(etwork/nknown3estination>ost/nknown3estination(etworkA&ministrativelyrohibite&3estination>ost

A&ministrativelyrohibite&

:

/edirect3 *ch#55 L*xceeded

'he two most common trou&leshooting tools thatutili#e I)7 are 6 PacketInternetr#.er!.ing&6 racer#ute

Pingis a core connecti,ity trou&leshooting tool+ whichutili#es the "cho @equest and "cho @e*ly I)7 messages todetermine if an I7 address is reacha&le and res*onding.7ing will additionally *ro,ide the r#und-tri.time&etweenthe source and destination+ usually measured inmilliseconds.


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internet protocol suite and all its interface

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