IP Subnettin IP Subnetting - International Journal of Electronics ...

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24 Οκτ 2013 (πριν από 4 χρόνια και 17 μέρες)

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IIn ntte er rn na attiio on na all J Jo ou ur rn na all o off E Elle ec cttr ro on niic cs s,, C Co om mm mu un niic ca attiio on n & & S So offtt C Co om mp pu uttiin ng g S Sc ciie en nc ce e a an nd d Engineering
ISSN: 2277-9477, Volume 2, Issue 5


I IP P S Su ub bn ne et tt ti in ng g

Shailesh N. Sisat Prajkta S. Bhopale V Vi is sh hw wa aj ji it t K K.. B Ba ar rb bu ud dh he e


s sp pe ec ci if fi ic c l lo oc ca at ti io on n o of f a a d de ev vi ic ce e o on n t th he e n ne et tw wo or rk k.. An IP address
Abstract - Network m ma an na ag ge em me en nt t b be ec co om me es s m mo or re e a an nd d m mo or re e
is a 32-b bi it t n nu um mb be er r t ty yp pi ic ca al ll ly y r re ep pr re es se en nt te ed d i in n f fo ou ur r s se ec ct ti io on ns s
important as computer-n ne et tw wo or rk ks s g gr ro ow w s st te ea ad di il ly y.. A A c cr ri it ti ic ca al l s sk ki il ll l
called octets. These sections are e s se eg gr re eg ga at te ed d b by y a a d do ot t called
f fo or r a an ny y n ne et tw wo or rk k a ad dm mi in ni is st tr ra at to or r o or r s se ec cu ur ri it ty y a ad dm mi in n t th ha at t s su up pp po or rt ts s
a as s d do ot tt te ed d d de ec ci im ma al l r re ep pr re es se en nt ta at ti io on n. A sample IP address is
a a n ne et tw wo or rk k e en nv vi ir ro on nm me en nt t i is s I IP P S Su ub bn ne et tt ti in ng g.. T Th hi is s k kn no ow wl le ed dg ge e c ca an n
1 17 72 2..1 16 6..1 10 0..1 15 5.. T Th hi is s I IP P a ad dd dr re es ss s i is s w wh ha at t identifies a system or
be gained by different methods and it is n ne ee ed de ed d i in n different
resource on a particular I IP P n ne et tw wo or rk k.. The IP address itself is
point of views. These individual l v vi ie ew ws s a ar ri is se e f fr ro om m distinct needs
a ac ct tu ua al ll ly y m ma ad de e u up p o of f t tw wo o p pa ar rt ts s.. O On ne e p pa ar rt t i id de en nt ti if fi ie es s t th he e
o of f p pe er rs so on ns s,, w wh ho o a ar re e i in nv vo ol lv ve ed d i in n n ne et tw wo or rk k m ma an na ag ge em me en nt t.. T Th he e
network that the host b be el lo on ng gs s t to o,, a an nd d t th he e o ot th he er r p pa ar rt t i id de en nt ti if fi ie es s
f fo ol ll lo ow wi in ng g u us se e c ca as se es s r re ep pr re es se en nt t s se el le ec ct te ed d g gr ro ou up ps s o of f m ma an na ag ge er rs s o or r
engineers. They are not complete, but should increase the host. To figure out where
c co om mp pr re eh he en ns si io on n o of f t th he e c co om mp pl le ex xi it ty y o of f n ne et tw wo or rk k d di is sc co ov ve er ry. This
t th he e n ne et tw wo or rk k p po or rt ti io on n s st to op ps s a an nd d t th he e host part begins you need
p pa ap pe er r d di is sc cu us ss se es s w wh hy y s su ub bn ne et tt ti in ng g i is s i im mp po or rt ta an nt t,, I IP P a ad dd dr re es ss si in ng g
a a s su ub bn ne et t m ma as sk k.. A A s su ub bn ne et t m ma as sk k i is s a al ls so o r re ep pr re es se en nt te ed d i in n d do ot tt te ed d
b ba as si ic cs s,, d de ec ci im ma al l t to o b bi in na ar ry y c co on nv ve er rs si io on n a an nd d e ea ar rl ly y s su ub bn ne et tt ti in ng g..
decimal notation. W Wh he en n y yo ou u s se ee e an IP address, you will

always see another n nu um mb be er r a as ss so oc ci ia at te ed d w wi it th h t th he e I IP P a ad dd dr re es ss s
Keywords: TCP/IP, IP Subnetting, C Cl la as ss s o of f n ne et tw wo or rk k
t th ha at t l lo oo ok ks s s so om me et th hi in ng g l li ik ke e o on ne e o of f t th he e f fo ol ll lo ow wi in ng g: :

• 255.0.0.0
I. INTRODUCTION
• 255.255.0.0
T Th hi is s a ar rt ti ic cl le e i is s f fo oc cu us si in ng g o on n t th he e b ba as si ic cs s o of f S Su ub bn ne et tt ti in ng g.. W Wh hi il le e
• 255.255.255.0
using I IP P a ad dd dr re es ss s i it t i is s v ve er ry y e ea as sy y t to o b br re ea ak k i it t i in n t to o s su ub bn ne et ts s s so o
T Th hi is s n nu um mb be er r i is s c ca al ll le ed d a as s s su ub bn ne et t m ma as sk k.. Following figure
that the one network address c ca an n b be e u us se ed d f fo or r m mo or re e t th ha an n o on ne e
shows an IP header
networks, T Th he e t th he eo or ry y c ca al ll le ed d a as s S Su ub bn ne et tt ti in ng g.. S Su ub bn ne et tt ti in ng g

a al ll lo ow ws s u us s t to o b br re ea ak k a a l la ar rg ge e n ne et tw wo or rk k i in nt to o a a b bu un nc ch h o of f s sm ma al ll le er r
Header Type of
Version Total length
networks. If an o or rg ga an ni iz za at ti io on n i is s l la ar rg ge e o or r i if f i it ts s c co om mp pu ut te er rs s a ar re e
Length service
(4) (16)
g ge eo og gr ra ap ph hi ic ca al ll ly y d di is sp pe er rs se ed d,, i it t m ma ak ke es s g go oo od d s se en ns se e t to o d di iv vi id de e
(4) (8)
n ne et tw wo or rk k i in nt to o s sm ma al ll le er r o on ne es s c co on nn ne ec ct te ed d t to og ge et th he er r b by y r ro ou ut te er rs s..
Flags Fragment offset
Identification (16)
Subnetting is important for several reasons.
(3) (13)
• Reduced Network Traffic: B By y s su ub bn ne et tt ti in ng g
Protocol
Time to live (8) Header checksum (16)
the network w we e c ca an n p pa ar rt ti it ti io on n i it t t to o a as s m ma an ny y s sm ma al ll le er r n ne et tw wo or rk ks s
(8)
a as s w we e n ne ee ed d a an nd d t th hi is s a al ls so o h he el lp ps s r re ed du uc ce e t tr ra af ff fi ic c a an nd d h hi id de es s t th he e
Source IP address (32)
complexity of the network.
• Optimized network performance:
Destination IP address (32)
Reduced n ne et tw wo or rk k t tr ra af ff fi ic c r re es su ul lt ts s i in n o op pt ti im mi iz ze ed d n ne et tw wo or rk k
performance.
O Op pt ti io on ns s + + P Pa ad dd di in ng g ( (0 0 o or r 3 32 2 i if f a an ny y) )
• Simplified management: qu ui ic ck kl ly y i id de en nt ti if fy y
a an nd d r re es so ol lv ve e n ne et tw wo or rk k p pr ro ob bl le em m i in n a a b bu un nc ch h o of f s sm ma al ll le er r n ne et tw wo or rk ks s

than within a single big network.
The fields are as follows.
• S Se ec cu ur ri it ty y: : S Su ub bn ne et tt ti in ng g c ca an n h he el lp p e en ns su ur re e
• Version: IP version number.
n ne et tw wo or rk k s se ec cu ur ri it ty y b by y f fa ac ci il li it ta at ti in ng g c co om mm mu un ni ic ca at ti io on n b be et tw we ee en n
• H He ea ad de er r l le en ng gt th h: : H He ea ad de er r l le en ng gt th h i in n 3 32 2-bit words.
c co om mp pu ut te er rs s o on n t th he e s sa am me e s su ub bn ne et t w wh hi il le e p pr re ev ve en nt ti in ng g a ac cc ce es ss s from
• T Ty yp pe e o of f s se er rv vi ic ce e: : T Ty yp pe e o of f s se er rv vi ic ce e t te el ll ls s h ho ow w t th he e d da at ta ag gr ra am m
computers on other subnets.
s sh ho ou ul ld d b be e h ha an nd dl le ed d.. T Th he e f fi ir rs st t t th hr re ee e b bi it ts s a ar re e t th he e p pr ri io or ri it ty y bits
• Facilitates spanning of large
which are n no ow w c ca al ll le ed d t th he e d di if ff fe er re en nt ti ia at te ed d s se er rv vi ic ce es s b bi it ts s..
Geographical d di is st ta an nc ce e: : B Be ec ca au us se e W WA AN N links are
• T To ot ta al l l le en ng gt th h: : L Le en ng gt th h o of f t th he e p pa ac ck ke et t i in nc cl lu ud di in ng g h he ea ad de er r a an nd d
c co om mp pa ar ra at ti iv ve el ly y s sl lo ow we er r a an nd d m mo or re e e ex xp pe en ns si iv ve e t th ha an n L LA AN N l li in nk ks s,, a a
data.
s si in ng gl le e l la ar rg ge e n ne et tw wo or rk k t th ha at t s sp pa an ns s l lo on ng g d di is st ta an nc ce es s c ca an n c cr re ea at te e
• Identification: Unique IP- p pa ac ck ke et t v va al lu ue e u us se ed d t to o
p pr ro ob bl le em ms s i in n e ev ve er ry y a ar re ea a.. C Co on nn ne ec ct ti in ng g m mu ul lt ti ip pl le e s sm ma al ll le er r
d di if ff fe er re en nt ti ia at te e f fr ra ag gm me en nt te ed d p pa ac ck ke et ts s f fr ro om m d di if ff fe er re en nt t d da at ta ag gr ra am m..
networks makes the system more efficient.
• F Fl la ag gs s: : S Sp pe ec ci if fi ie es s w wh he et th he er r f fr ra ag gm me en nt ta at ti io on n s sh ho ou ul ld d o oc cc cu ur r..

• F Fr ra ag gm me en nt t o of ff fs se et t: : P Pr ro ov vi id de es s f fr ra ag gm me en nt ta at ti io on n a an nd d
Introduction to IP: Before we start dive in nt to o s su ub bn ne et tt ti in ng g,, w we e
r re ea as ss se em mb bl ly y i if f t th he e p pa ac ck ke et t i is s t to oo o l la ar rg ge e t to o p pu ut t i in n a a f fr ra am me e.. I It t a al ls so o
need to study s so om me e b ba as si ic cs s.. T Th he e f fi ir rs st t i it te em m f fo or r d di is sc cu us ss si io on n i is s
allow ws s d di if ff fe er re en nt t m ma ax xi im mu um m t tr ra an ns sm mi is ss si io on n u un ni it ts s o on n t th he e
the IP address. A An n I IP P a ad dd dr re es ss s i is s a a n nu um me er ri ic c i id de en nt ti if fi ie er r
internet.
a as ss si ig gn ne ed d t to o e ea ac ch h m ma ac ch hi in ne e o on n a an n I IP P n ne et tw wo or rk k.. I It t d de es si ig gn na at te es s t th he e
• Time to live: T Th hi is s f fi ie el ld d i in nd di ic ca at te es s t th he e m ma ax xi im mu um m t ti im me e t th he e
5
IIn ntte er rn na attiio on na all J Jo ou ur rn na all o off E Elle ec cttr ro on niic cs s,, C Co om mm mu un niic ca attiio on n & & S So offtt C Co om mp pu uttiin ng g S Sc ciie en nc ce e a an nd d Engineering
ISSN: 2277-9477, Volume 2, Issue 5


d da at ta ag gr ra am m i is s a al ll lo ow we ed d t to o r re em ma ai in n i in n t th he e i in nt te er rn ne et t s sy ys st te em m.. I If f t th hi is s 4. W Wr ri it te e d do ow wn n t th he e r re em ma ai in nd de er r t to o t th he e l le ef ft t o of f t th he e p pr re ev vi io ou us s
field contains the value z ze er ro o,, t th he en n t th he e d da at ta ag gr ra am m m mu us st t b be e remainder.
destroyed. This field is modified i in n i in nt te er rn ne et t h he ea ad de er r 5. R Re ep pe ea at t t th hi is s u un nt ti il l y yo ou u e en nd d u up p w wi it th h 0 0..
p pr ro oc ce es ss si in ng g.. T Th he e t ti im me e i is s m me ea as su ur re ed d i in n u un ni it ts s o of f seconds, but F Fo or r 1 17 72 2,, t th he e f fo or rm mu ul la a w wo ou ul ld d l lo oo ok k l li ik ke e t th hi is s: :
since every module that processes a d da at ta ag gr ra am m m mu us st t decrease 172 ÷ 2 = 86 remainder 0
t th he e T TT TL L b by y a at t l le ea as st t o on ne e e ev ve en n i if f i it t p pr ro oc ce es ss s t th he e d da at ta ag gr ra am m i in n 86 ÷ 2 = 43 remainder 0
l le es ss s t th ha an n a a s se ec co on nd d,, t th he e T TT TL L m mu us st t b be e t th ho ou ug gh ht t o of f only as an 43 ÷ 2 = 21 remainder 1
upper b bo ou un nd d o on n t th he e t ti im me e a a d da at ta ag gr ra am m m ma ay y e ex xi is st t.. T Th he e 21 ÷ 2 = 10 remainder 1
intention is to cause u un nd de el li iv ve er ra ab bl le e d da at ta ag gr ra am ms s t to o b be e 10 ÷ 2 = 5 remainder 0
d di is sc ca ar rd de ed d,, a an nd d t to o b bo ou un nd d t th he e m ma ax xi im mu um m d da at ta ag gr ra am m l li if fe et ti im me e.. 5 ÷ 2 = 2 remainder 1
2 ÷ 2 = 1 remainder 0
• Protocol: I In n t th he e I In nt te er rn ne et t P Pr ro ot to oc co ol l v ve er rs si io on n 4 4 ( (I IP Pv v4 4) )
1 ÷ 2 = 0 remainder 1
[RFC791] there is a field called "P Pr ro ot to oc co ol l" " t to o i id de en nt ti if fy y t th he e
n ne ex xt t l le ev ve el l p pr ro ot to oc co ol l.. T Th hi is s i is s a an n 8 8 b bi it t f fi ie el ld d.. I In n I In nt te er rn ne et t So b bi in na ar ry y n nu um mb be er r f fo or r 1 17 72 2 = = 1 10 01 10 01 11 10 00 0..
E Ea ac ch h s se ec ct ti io on n o of f a an n I IP P a ad dd dr re es ss s i is s 8 8 b bi it ts s l lo on ng g.. I In n t th he e p pr re ev vi io ou us s
P Pr ro ot to oc co ol l v ve er rs si io on n 6 6 ( (I IP Pv v6 6) ) [ [R RF FC C2 24 46 60 0] ],, t th hi is s f fi ie el ld d i is s c ca al ll le ed d t th he e
example, the conversion worked o ou ut t t to o 8 8 b bi it ts s e ex xa ac ct tl ly y,, s so o that
"Next Header" field.
w wa as s e ea as sy y.. I If f w we e u us se ed d a a s sm ma al ll le er r n nu um mb be er r s su uc ch h a as s 1 12 2, we would
• H He ea ad de er r c ch he ec ck ks su um m: : C Cy yc cl li ic c r re ed du un nd da an nc cy y c ch he ec ck k ( (C CR RC C) ) o on n
have r re ea ac ch he ed d 0 0 b be ef fo or re e w we e h ha ad d 8 8 b bi it ts s.. I If f t th hi is s o oc cc cu ur rs s,, f fi il ll l i in n t th he e
header only.
r re em ma ai in ni in ng g b bi it ts s w wi it th h 0 0s s.. F Fo or r e ex xa am mp pl le e: :
• Source IP address: 32-bit t I IP P a ad dd dr re es ss s o of f s se en nd di in ng g s st ta at ti io on n..
12 ÷ 2 = 6 remainder 0
• Destination IP address: 32-b bi it t I IP P a ad dd dr re es ss s o of f t th he e s st ta at ti io on n
6 ÷ 2 = 3 remainder 0
this packet is destined for.
3 ÷ 2 = 1 remainder 1
• O Op pt ti io on ns s: : U Us se ed d f fo or r n ne et tw wo or rk k t te es st ti in ng g,, d de eb bu ug gg gi in ng g,, s se ec cu ur ri it ty y..
1 ÷ 2 = 0 remainder 1
E En nc co od de es s t th he e o op pt ti io on ns s r re eq qu ue es st te ed d b by y t th he e s se en nd di in ng g u us se er r..
B Be ec ca au us se e w we e g go ot t t to o 0 0 i in n o on nl ly y f fo ou ur r s st te ep ps s,, t th he e r re em ma ai in ni in ng g b bi it ts s

are 0---s so o t th he e b bi in na ar ry y o of f 1 12 2 i is s 0 00 00 00 01 11 10 00 0..
II. DECIMAL AND BI IN NA AR RY Y

I In n I IP P s su ub bn ne et tt ti in ng g,, i it t i is s i im mp po or rt ta an nt t t th ha at t w we e k kn no ow w h ho ow w t to o
III. IP TE ER RM MI IN NO OL LO OG GY Y
c co on nv ve er rt t I IP P a ad dd dr re es ss se es s a an nd d s su ub bn ne et t m ma as sk ks s f fr ro om m t th he ei ir r d de ec ci im ma al l
• N Ne et tw wo or rk k a ad dd dr re es ss s: : T Th hi is s i is s t th he e d de es si ig gn na at ti io on n u us se ed d i in n
f fo or rm m t to o t th he e b bi in na ar ry y f fo or rm m b be ec ca au us se e t th he e l lo oc ca at ti io on ns s o of f t th he e 1 1s s a an nd d
r ro ou ut ti in ng g t to o s se en nd d p pa ac ck ke et ts s t to o a a r re em mo ot te e n ne et tw wo or rk k.. for example,
0s is extremely important.
1 10 0..0 0..0 0..0 0,,1 17 72 2..1 16 6..0 0..0 0 a an nd d 1 19 92 2..1 16 68 8..0 0..0 0
I If f w we e u us se e t th he e s sa am mp pl le e I IP P a ad dd dr re es ss s f fr ro om m b be ef fo or re e,, 1 17 72 2..1 16 6..1 10 0..1 15 5,,
• Broadcast address: T Th he e a ad dd dr re es ss s u us se ed d b by y a ap pp pl li ic ca at ti io on ns s
a an nd d r re ep pr re es se en nt t i it t i in n b bi in na ar ry y f fo or rm ma at t,, i it t w wo ou ul ld d l lo oo ok k l li ik ke e t th hi is s: :
a an nd d h ho os st ts s t to o s se en nd d i in nf fo or rm ma at ti io on n t to o a al ll l n no od de es s o on n a a n ne et tw wo or rk k i is s
1 10 01 10 01 11 10 00 0..0 00 00 01 10 00 00 00 0..0 00 00 00 00 01 10 01 10 0..0 00 00 00 01 11 11 11 1.. S So o,, h ho ow w d do o w we e
called the b br ro oa ad dc ca as st t a ad dd dr re es ss s. Example include
g ge et t f fr ro om m t th he e d de ec ci im ma al l f fo or rm m t to o t th he e b bi in na ar ry y f fo or rm m,, a an nd d v vi ic ce e
2 25 55 5..2 25 55 5..2 25 55 5..2 25 55 5,, w wh hi ic ch h i is s a an ny y n ne et tw wo or rk k,, a al ll l n no od de es s; ;
versa?
1 17 72 2..1 16 6..2 25 55 5..2 25 55 5,, w wh hi ic ch h i is s a al ll l s su ub bn ne et ts s a an nd d h ho os st ts s o on n n ne et tw wo or rk k
F Fi ir rs st t,, l le et t’ ’s s c co on nv ve er rt t f fr ro om m b bi in na ar ry y t to o d de ec ci im ma al l.. I If f w we e t ta ak ke e t th he e
1 17 72 2..1 16 6..0 0..0 0; ; a an nd d 1 10 0..2 25 55 5..2 25 55 5..2 25 55 5,, w wh hi ic ch h b br ro oa ad dc ca as st ts s t to o a al ll l
first octet of our sa am mp pl le e I IP P a ad dd dr re es ss s a an nd d m ma ap p i it t t to o t th he e b bi in na ar ry y
s su ub bn ne et ts s a an nd d h ho os st ts s o on n n ne et tw wo or rk k1 10 0..0 0..0 0..0 0
numbering system, it looks like this:
• Class of network: The d de es si ig gn ne er r o of f t th he e Internet decided

0
7 6 5 4 3 2 1
t to o c cr re ea at te e c cl la as ss se es s o of f n ne et tw wo or rk k b ba as se ed d o on n n ne et tw wo or rk k s si iz ze e,, f fo or r t th he e
Binary 2
2 2 2 2 2 2 2

s sm ma al ll l n nu um mb be er r o of f n ne et tw wo or rk ks s p po os ss se es ss si in ng g a a v ve er ry y l la ar rg ge e n nu um mb be er r
=1
=128 =64 =32 =16 =8 =4 =2
o of f n no od de es s,, t th he ey y c cr re ea at te ed d t th he e r ra an nk k Class A network. At the
IP
1 0 1 0 1 1 0 0
other extreme is the C Cl la as ss s C C n ne et tw wo or rk k, which is reserved for
address
t th he e n nu um me er ro ou us s n ne et tw wo or rk ks s w wi it th h a a s sm ma al ll l n nu um mb be er r o of f n no od de es s.. The

c cl la as ss s d di is st ti in nc ct ti io on n f fo or r n ne et tw wo or rk ks s b be et tw we ee en n v ve er ry y l la ar rg ge e a an nd d v ve er ry y
N No ow w a al ll l w we e h ha av ve e t to o d do o i is s a ad dd d t th he e d de ec ci im ma al l n nu um mb be er rs s t to og ge et th he er r
small is predictably called the C Cl la as ss s B B n ne et tw wo or rk k..
w wh he er re e a a 1 1 a ap pp pe ea ar rs s a an nd d w we e w wi il ll l g ge et t t th he e d de ec ci im ma al l e eq qu ui iv va al le en nt t o of f
S Su ub bd di iv vi id di in ng g a an n I IP P a ad dd dr re es ss s i in nt to o a a n ne et tw wo or rk k a an nd d
t th he e b bi in na ar ry y n nu um mb be er r.. I In n t th hi is s c ca as se e i it t l lo oo ok ks s l li ik ke e t th hi is s: :
node e a ad dd dr re es ss s i is s d de et te er rm mi in ne ed d b by y t th he e c cl la as ss s d de es si ig gn na at ti io on n o of f o on ne e’ ’s s
128 + 32 + 8 + 4 = 172.
n ne et tw wo or rk k.. F Fo ol ll lo ow wi in ng g f fi ig g s su um mm ma ar ri iz ze es s t th he e t th hr re ee e c cl la as ss se es s o of f
Now let’s convert from binary to decimal. l le et t’ ’s s take our 172
networks.
e ex xa am mp pl le e f fr ro om m p pr re ev vi io ou us sl ly y.. T Th he e f fo or rm mu ul la a f fo or r c co on nv ve er rs si io on n i is s a as s
8 8b bi it ts s 8 8b bi it ts s 8 8b bi it ts s 8 8b bi it ts s
follows.
Class A: Network Host Host Host
1. F Fi ir rs st t d di iv vi id de e t th he e n nu um mb be er r b by y 2 2.. T Th he e r re em ma ai in nd de er r w wi il ll l b be e e ei it th he er r

0 or 1.
Class B: Network N Ne et tw wo or rk k Host Host
2. Write down the remainder.

3. D Di iv vi id de e t th he e r re em ma ai in ni in ng g n nu um mb be er r w wi it th ho ou ut t t th he e r re em ma ai in nd de er r b by y 2 2..
Class C: Network N Ne et tw wo or rk k Network Host
Again, the remainder will be either 1 or 0.

6
IIn ntte er rn na attiio on na all J Jo ou ur rn na all o off E Elle ec cttr ro on niic cs s,, C Co om mm mu un niic ca attiio on n & & S So offtt C Co om mp pu uttiin ng g S Sc ciie en nc ce e a an nd d Engineering
ISSN: 2277-9477, Volume 2, Issue 5


Class D: Multicast
Class E: Research


Default Subnet
T Th he e d de et te er rm mi in na at ti io on n o of f w wh hi ic ch h c cl la as ss s a a p pa ar rt ti ic cu ul la ar r n ne et tw wo or rk k f fe el ll l i in n
Class Format
Mask
w wa as s d de et te er rm mi in ne ed d b by y t th he e f fi ir rs st t o oc ct te et t o of f t th he e I IP P a ad dd dr re es ss s,,
A network.node.node.node 255.0.0.0
specifically by t th he e f fi ir rs st t f fe ew w b bi it ts s o of f t th he e f fi ir rs st t o oc ct te et t.. T Th hi is s i is s
B network.networ.node..n no od de e 255.255.0.0
represented in the following table.
C ne et tw wo or rk k..n ne et tw wo or r..n ne et tw wo or rk k..n no od de e 255.255.255.0
st
1 Octet N Nu um mb be er r o of f Hosts per
First Bits
Classless Inter Domain Routing (C CI ID DR R) ): :
n ne et tw wo or rk ks s network
C CI ID DR R i is s t th he e m me et th ho od d t th ha at t I IS SP P ( (I In nt te er rn ne et t s se er rv vi ic ce e p pr ro ov vi id de er rs s) ) u us se e
Class A 0 1-126 126 16,777,214
t to o a al ll lo oc ca at te e a a n nu um mb be er r o of f a ad dd dr re es ss se es s t to o a a c co om mp pa an ny y o or r a a
Class B 10 128-191 16,384 65,534
c cu us st to om me er r.. I IS SP P p pr ro ov vi id de e a ad dd dr re es ss se es s i in n a a c ce er rt ta ai in n b bl lo oc ck k size. for
Class C 110 192-223 2 2,,0 09 97 7,,1 15 52 2 254
example 192.168.10.32/28. W We e m ma ay y i id de en nt ti if fy y t th he e s su ub bn ne et t
Class D 1110 224-239 n/a n/a
mask from this block size. T Th he e s sl la as sh h n no ot ta at ti io on n ( (/ /) ) m me ea an ns s h ho ow w
Class E 11110 240-254 n/a n/a
many bits out of 32 bits a ar re e t tu ur rn ne ed d o on n ( (1 1s s) )..

f fo or r e ex xa am mp pl le e ,, a a C Cl la as ss s C C d de ef fa au ul lt t m mask would be
T Th he e n ne et tw wo or rk k I ID D c ca an nn no ot t b be e 1 12 27 7.. T Th he e 1 12 27 7..0 0..0 0..0 0 n ne et tw wo or rk k i is s
2 25 55 5..2 25 55 5..2 25 55 5..0 0,, w wh hi ic ch h i is s / /2 24 4 b be ec ca au us se e 2 24 4 b bi it ts s a ar re e o on ne es s ( (1 1s s) ),,
reserved for loop-b ba ac ck k a an nd d w wa as s o or ri ig gi in na al ll ly y d de es si ig gn ne ed d f fo or r
1 11 11 11 11 11 11 11 1..1 11 11 11 11 11 11 11 1..1 11 11 11 11 11 11 11 1..0 0
testing purposes. Class D and E a ar re e s sp pe ec ci ia al l classes; in this
F Fo ol ll lo ow wi in ng g t ta ab bl le e s sh ho ow ws s e ev ve er ry y a av va ai il la ab bl le e s su ub bn ne et t m ma as sk k a an nd d i it ts s
article discussion is focus on C Cl la as ss se es s A A,, B B,, a an nd d C C.. E Ea ac ch h o of f
equivalent CIDR slash notation.
t th he es se e c cl la as ss se es s h ha as s a a d de ef fa au ul lt t s su ub bn ne et t m ma as sk k a an nd d a a p pr ri iv va at te e a ad dd dr re es ss s

range.
Subnet Mask CIDR S Su ub bn ne et t M Ma as sk k CIDR

Value Value
Private Addresses: The address can be p pu ub bl li ic c ( (i i..e e..,, u un ni iq qu ue e) )
255.0.0.0 /8 2 25 55 5..2 25 55 5..2 24 40 0..0 0 /20
or private. In today’s enterprise networks,, p pr ri iv va at te e addressing
255.128.0.0 /9 2 25 55 5..2 25 55 5..2 24 48 8..0 0 /21
is commonly used because of the address s sh ho or rt ta ag ge e i in n I IP Pv v4 4..
255.192.0.0 /10 2 25 55 5..2 25 55 5..2 25 52 2..0 0 /22
In enterprise networks private a ad dd dr re es ss si in ng g i is s p pr re ef fe er rr re ed d
255.224.0.0 /11 2 25 55 5..2 25 55 5..2 25 54 4..0 0 /23
because it provides s se ec cu ur re e a ac cc ce es ss s r ra at th he er r t th ha an n o op pe en n a an nd d
public access to the enterprise network. T Th he e p pr ri iv va at te e a ad dd dr re es ss s 255.240.0.0 /12 2 25 55 5..2 25 55 5..2 25 55 5..0 0 /24
ranges are util li iz ze ed d o on n i in nt te er rn na al l n ne et tw wo or rk ks s,, a an nd d addresses in 255.248.0.0 /13 2 25 55 5..2 25 55 5..2 25 55 5..1 12 28 8 /25
t th he es se e r ra an ng ge es s c ca an nn no ot t b be e r ro ou ut te ed d i in n t th he e p pu ub bl li ic c n ne et tw wo or rk k o of f t th he e
255.252.0.0 /14 2 25 55 5..2 25 55 5..2 25 55 5..1 19 92 2 /26
I In nt te er rn ne et t.. T Th he es se e d de ef fa au ul lt ts s a an nd d p pr ri iv va at te e r ra an ng ge es s a ar re e s sh ho ow wn n h he er re e: :
255.254.0.0 /15 2 25 55 5..2 25 55 5..2 25 55 5..2 22 24 4 /27

255.255.0.0 /16 2 25 55 5..2 25 55 5..2 25 55 5..2 24 40 0 /28
Default Subnet
255.255.128.0 /17 2 25 55 5..2 25 55 5..2 25 55 5..2 24 48 8 /29
Class P Pr ri iv va at te e A Ad dd dr re es ss s R Ra an ng ge e
Mask
255.255.192.0 /18 2 25 55 5..2 25 55 5..2 25 55 5..2 25 52 2 /30
Class A 255.0.0.0 10.0.0.0 - 1 10 0..2 25 55 5..2 25 55 5..2 25 55 5
255.255.224.0 /19
Class B 255.255.0.0 172.16.0.0 - 1 17 72 2..3 31 1..2 25 55 5..2 25 55 5

Class C 255.255.255.0 192.168.0.0 - 1 19 92 2..1 16 68 8..2 25 55 5..2 25 55 5
T Th he e l la ar rg ge es st t m ma as sk k a av va ai il la ab bl le e ( (r re eg ga ar rd dl le es ss s o of f t th he e c cl la as ss s o of f

a ad dd dr re es ss s) ) c ca an n o on nl ly y b be e a a / /3 30 0 b be ec ca au us se e a at t least 2 bits for host
Subnetting the network: A A l la ar rg ge e n ne et tw wo or rk k i is s d di iv vi id de ed d i in nt to o a a
bits are required.
s sm ma al ll le er r n ne et tw wo or rk k t th he e p pr ro oc ce es ss s i is s k kn no ow wn n a as s S Su ub bn ne et tt ti in ng g a an nd d t th he e
T Th he e / /8 8 t th hr ro ou ug gh h / /1 15 5 c ca an n o on nl ly y b be e u us se ed d w wi it th h C Cl la as ss s A A n ne et tw wo or rk k
smaller network is k kn no ow wn n a as s s su ub bn ne et tw wo or rk k o or r s su ub bn ne et t..
a ad dd dr re es ss se es s.. / /1 16 6 t th hr ro ou ug gh h / /2 23 3 c ca an n b be e u us se ed d b by y C Cl la as ss s A A a an nd d B B
T To o c cr re ea at te e s su ub bn ne et tw wo or rk ks s,, t ta ak ke e b bi it ts s f fr ro om m t th he e h ho os st t p po or rt ti io on n o of f t th he e
n ne et tw wo or rk k a ad dd dr re es ss se es s.. / /2 24 4 t th hr ro ou ug gh h / /3 30 0 c ca an n b be e u us se ed d b by y C Cl la as ss s A A,,
I IP P a ad dd dr re es ss s a an nd d r re es se er rv ve e t th he em m t to o d de ef fi in ne e t th he e s su ub bn ne et t a ad dd dr re es ss s..
B, and C network addresses.
T Th hi is s m me ea an ns s f fe ew we er r b bi it ts s f fo or r h ho os st ts s,, s so o t th he e m mo or re e s su ub bn ne et ts s,, t th he e
Hosts and route er rs s u us se e B Bo oo ol le ea an n m ma at th h t to o d de et te er rm mi in ne e t th he e n ne et ti id d
fewer bits available for defining hosts.
a an nd d t th he e h ho os st ti id d a an nd d t th he e h ho os st te ed d b by y t th he e u us se e o of f A AN ND Di in ng g..


Subnet Mask: I In n o or rd de er r t to o r re ed du uc ce e t th he e c co on nj ju un nc ct ti io on n,, n ne et tw wo or rk k i is s
Bit1 Bit2 Result
l lo og gi ic ca al ll ly y b br re ea ak k i in nt to o p pi ie ec ce es s.. N Ne et tm ma as sk k i is s m me ec ch ha an ni is su um m,, w we e
0 0 0
h ha av ve e t to o u us se e i it t t to o i id de en nt ti if fy y t th he e r ra an ng ge e o of f I IP P t to o c cr re ea at te e a a
0 1 0
network.A A s su ub bn ne et t m ma as sk k i is s a a 3 32 2 b bi it t v va al lu ue e t th ha at t a al ll lo ow ws s t th he e
1 0 0
recipient of IP packets to distingu ui is sh h t th he e n ne et tw wo or rk k I ID D p po or rt ti io on n
1 1 1
o of f t th he e I IP P a ad dd dr re es ss s f fr ro om m t th he e h ho os st t I ID D p po or rt ti io on n o of f t th he e I IP P a ad dd dr re es ss s..

F Fo ol ll lo ow wi in ng g t ta ab bl le e s sh ho ow ws s t th he e d de ef fa au ul lt t s su ub bn ne et t m ma as sk ks s f fo or r c cl la as ss s A A,,

B and C.

7
IIn ntte er rn na attiio on na all J Jo ou ur rn na all o off E Elle ec cttr ro on niic cs s,, C Co om mm mu un niic ca attiio on n & & S So offtt C Co om mp pu uttiin ng g S Sc ciie en nc ce e a an nd d Engineering
ISSN: 2277-9477, Volume 2, Issue 5


Simple steps in Subnetting: S Su ub bn ne et t m ma as sk k = = 2 25 55 5..2 25 55 5..255.240
 Identify Class of network w wh ha at t i is s t th he e s su ub bn ne et t a an nd d b br ro oa ad dc ca as st t a ad dd dr re es ss s o of f t th he e n ne et tw wo or rk k of
 Default Net mask w wh hi ic ch h t th he e a ab bo ov ve e a ad dd dr re es ss s i is s a a m me em mb be er r?
(number of stolen bits)

• Number of networks = 2
st
( (a av va ai il la ab bl le e b bi it t – stolen bit)
 1 s st te ep p: : i id de en nt ti if fy y c cl la as ss s o of f n ne et tw wo or rk k
• Number of hosts per network= 2 – 2
It’s a Class C n ne et tw wo or rk k

nd
 2 s st te ep p: : D De ef fa au ul lt t s su ub bn ne et t m ma as sk k
Subnetting a Class C address:
255.255.255.0


Example: Network address = 192.168.10.0

Subnet mask = 255.255.255.192
49=32+1 16 6+1

st
2 24 40 0= =1 12 28 8+ +6 64 4+ +3 32 2+ +1 16 6
 1 step: identify class of network

It’s a Class C network
nd
 2 step: Default subnet mask 128 64 32 16 8 4 2 1
255.255.255.0 49 0 0 1 1 0 0 0 1
240 1 1 1 1 0 0 0 0


192=128+64 0 0 1 1 0 0 0 0



128 64 32 16 8 4 2 1 3 32 2+ +1 16 6= =4 48 8
R Re es su ul lt t o of f a ab bo ov ve e A AN ND D o op pe er ra at ti io on n i is s z ze er ro o 4 48 8 h he en nc ce e t th he e f fi ir rs st t I IP P
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
address is 192.168.10.48
192 1 1 0 0 0 0 0 0 0 0 0 0 0 0


rd (number of stolen bits)
 3 step: Number of subn ne et tw wo or rk ks s = = 2 2
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0


4
2 = 16 subnets
R Re es su ul lt t o of f a ab bo ov ve e A AN ND D o op pe er ra at ti io on n i is s z ze er ro o ( (0 0) ) h he en nc ce e t th he e f fi ir rs st t I IP P
th
 4 step:
address is 192.168.10.0
(available bit – stolen bit)
N Nu um mb be er r o of f h ho os st ts s p pe er r n ne et tw wo or rk k= = 2 2 – 2

rd ( (n nu um mb be er r o of f s st to ol le en n b bi it ts s) )

 3 step: Number of subnetworks = 2
(8-4)

= 2 -2
2
= 14 hosts
2 = 4 subnets
th

 4 step:
( (a av va ai il la ab bl le e b bi it t – stolen bit)
N No ow w w we e k kn no ow w t th he e p po os ss si ib bl le e s su ub bn ne et ts s a ar re e 1 16 6.. N No ow w k ke ee ep p
Number of hosts per subnetwork= 2 –
a ad dd di in ng g 1 16 6 u un nt ti il l w we e p pa as ss s t th he e h ho os st t a ad dd dr re es ss s 4 49 9,, s st ta ar rt ti in ng g f fr ro om m
2
zero.0, 16,32,48,64, and so on. T Th he e h ho os st t a ad dd dr re es ss s o of f 4 49 9 i is s

(8-2)
b be et tw we ee en n 4 48 8 a an nd d 6 64 4 s so o t th he e s su ub bn ne et t i is s 4 48 8..
= 2 -2

= 62 hosts
st
a) 192.168.10.48 1 s su ub bn ne et t I IP P

st
st
b) 192.168.10.49 1 v va al li id d h ho os st t I IP P
a) 192.168.10.0 1 subnet IP
st
c) 1 19 92 2..1 16 68 8..1 10 0..6 62 2 l la as st t v va al li id d h ho os st t
b) 192.168.10.1 1 valid host IP
d) 1 19 92 2..1 16 68 8..1 10 0..6 63 3 b br ro oa ad dc ca as st t I IP P
c) 192.168.10.62 last valid host

d) 192.168.10.63 broadcast IP
Subnetting a Class B address:
S Si im mi il la ar rl ly y t th he e f fo ol ll lo ow wi in ng g t ta ab bl le e s sh ho ow ws s t th he e a al ll l p po os ss si ib bl le e s su ub bn ne et ts s,,

t th he e v va al li id d h ho os st t r ra an ng ge es s o of f e ea ac ch h,, a an nd d t th he e b br ro oa ad dc ca as st t a ad dd dr re es ss s o of f
Example: : N Ne et tw wo or rk k a ad dd dr re es ss s = = 1 17 72 2..1 16 6.0.0
each subnet.
S Su ub bn ne et t m ma as sk k = = 2 25 55 5..2 25 55 5..128.0


subnet IP x.x.x.0 x.x.x.64 x x..x x..x x..128 x.x.x.192
st
st
1 step: identify class of network
1 valid host x.x.x.1 x.x.x.65 x x..x x..x x..129 x.x.x.193
It’s a Class B network
IP
nd
2 step: Default subnet mask
last valid x.x.x.62 x.x.x.126 x x..x x..x x..190 x.x.x.254
255.255.0.0
host

Broadcast IP x.x.x.63 x.x.x.127 x x..x x..x x..191 x.x.x.255
128


Example: Network address = 192.168.10.49
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IIn ntte er rn na attiio on na all J Jo ou ur rn na all o off E Elle ec cttr ro on niic cs s,, C Co om mm mu un niic ca attiio on n & & S So offtt C Co om mp pu uttiin ng g S Sc ciie en nc ce e a an nd d Engineering
ISSN: 2277-9477, Volume 2, Issue 5


128 64 32 16 8 4 2 1
AUTHOR’S PR RO OF FI IL LE E
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

128 1 0 0 0 0 0 0 0 0 0 0 0 0 0
Shailesh N. Sisat i is s a a m ma as st te er r d de eg gr re ee e c ca an nd di id da at te e i in n E El le ec ct tr ro on ni ic cs s & &
T Te el le ec co om mm mu un ni ic ca at ti io on n E En ng gi in ne ee er ri in ng g o of f S SG GB B A Am mr ra av va at ti i University,

Maharashtra, India.. H He e r re ec ce ei iv ve ed d h hi is s B B.E. degree in Electronics &
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
T Te el le ec co om mm mu un ni ic ca at ti io on n E En ng gi in ne ee er ri in ng g f fr ro om m S SG GB B A Am mr ra av va at ti i U Un ni iv ve er rs si it ty y.. H He e i is s

Red Hat Certified Engineer having i in nd du us st tr ri ia al l e ex xp pe er ri ie en nc ce e i in n n ne et tw wo or rk ki in ng g
Result of above AND o op pe er ra at ti io on n i is s z ze er ro o ( (0 0) ) h he en nc ce e t th he e f fi ir rs st t I IP P
industry
address is 172.16.0.0

Prajkta S. Bhopale is a master d de eg gr re ee e c ca an nd di id da at te e i in n E El le ec ct tr ro on ni ic cs s & &
rd ( (n nu um mb be er r o of f s st to ol le en n b bi it ts s) )
T Te el le ec co om mm mu un ni ic ca at ti io on n E En ng gi in ne ee er ri in ng g o of f S SG GB B A Am mr ra av va at ti i U Un ni iv ve er rs si it ty y M Ma ah ha ar ra as sh ht tr ra a,
 3 step: Number of subnetworks = 2
India. She received her B.E. d de eg gr re ee e i in n E El le ec ct tr ro on ni ic cs s & & T Te el le ec co om mm mu un ni ic ca at ti io on n
E En ng gi in ne ee er ri in ng g f fr ro om m S SG GB B A Am mr ra av va at ti i U Un ni iv ve er rs si it ty y..
1
2 = 2 subnets


Vishwajit K. Barbudhe i is s a a p pr ro of fe es ss so or r in the Department of

E El le ec ct tr ro on ni ic cs s & & T Te el le ec co om mm mu un ni ic ca at ti io on n E En ng gi in ne ee er ri in ng g,, A Ag gn ni ih ho ot tr ri i C C..O O..E E.. W Wa ar rd dh ha a,,
Nagpur University, Maharashtra, India.. H He e r re ec ce ei iv ve ed d h hi is s M M..T Te ec ch h d de eg gr re ee e i in n

th
E El le ec ct tr ro on ni ic cs s & & c co om mm mu un ni ic ca at ti io on n E En ng gi in ne ee er ri in ng g f fr ro om m P PI IT T C C..O O..E E.. R RG GP PV V
 4 step:
University, MP, India. He receiv ve ed d h hi is s B B.E. degree in Electronics &
( (a av va ai il la ab bl le e b bi it t – stolen bit)
Number of hosts per network= 2 – 2
T Te el le ec co om mm mu un ni ic ca at ti io on n E En ng gi in ne ee er ri in ng g f fr ro om m S SG GB B A Am mr ra av va at ti i U Un ni iv ve er rs si it ty y..


In this case, a av va ai il la ab bl le e b bi it ts s a ar re e a ad dd di it ti io on n o of f t th hi ir rd d a an nd d
fourth octet.
(16-1)
= 2 -2
= 32,766 hosts

subnet IP 172.16.0.0 1 17 72 2..1 16 6..1 12 28 8..0 0
st
1 valid host IP 172.16.0.1 1 17 72 2..1 16 6..1 12 28 8..1 1
last valid host 172.16.127.254 1 17 72 2..1 16 6..2 25 55 5..2 25 54 4
Broadcast IP 172.16.127.255 1 17 72 2..1 16 6..2 25 55 5..2 25 55 5


CONCLUSION
This article has discussed IP S Su ub bn ne et tt ti in ng g a as s i it t is an important
s sk ki il ll l t to o a ac cq qu ui ir re e b be ec ca au us se e i it t o of ff fe er rs s m ma an ny y b be en ne ef fi it ts s i in n a an ny y
n ne et tw wo or rk ke ed d e en nv vi ir ro on nm me en nt t.. U Us si in ng g t th he e i in nf fo or rm ma at ti io on n i in n this paper,
y yo ou u s sh ho ou ul ld d b be e a ab bl le e t to o s su ub bn ne et t a an ny y n ne et tw wo or rk k t to o take full
a ad dv va an nt ta ag ge e o of f t th he e I IP P a ad dd dr re es ss s s sp pa ac ce e y yo ou u u ut ti il li iz ze e..

REFERENCES

[1]Y. Rekhter et al., “Address Allocation for Private I In nt tr ra an ne et ts s,,” ” I IE ET TF F R RF FC C
1918, Feb. 1996.
[2] BEHCET SARIKAYA, “Home agent p pl la ac ce em me en nt t a an nd d I IP P a ad dd dr re es ss s
m ma an na ag ge em me en nt t f fo or r i in nt te eg gr ra at ti in ng g W WL LA AN NS S w wi it th h c ce el ll lu ul la ar r n ne et tw wo or rk ks s” ” 1 15 53 36 6-
1284/06/$20.00 © 2006 IEEE
[ [3 3] ] G G.. M Mo on nt te en ne eg gr ro o,, “ “R Re ev ve er rs se e T Tu un nn ne el li in ng g f fo or r M Mo ob bi il le e I IP P,,” ” IETF RFC 3024,
Jan. 2001.
[4] S. Vaarala et al.,, “ “M Mo ob bi il le e I IP Pv v4 4 T Tr ra av ve er rs sa al l A Ac cr ro os ss s I IP PS Se ec c b ba as sed VPN
Gateways,” Internet draft, Nov. 2005; h ht tt tp p: :/ // /i ie et tf fr re ep po or rt t..i is so oc c..o or rg g/ /a al ll l-ids/draft-
ietf-mip4-vpn-prob
lem-solution-02.txt
[5] ] B Bo ol lt t B Be er ra an ne ek k a an nd d N Ne ew wm ma an n,, " "S Sp pe ec ci if fi ic ca at ti io on n f fo or r t th he e I In nt te er rc co on nn ne ec ct ti io on n o of f a a
H Ho os st t a an nd d a an n I IM MP P,," " B BB BN N T Te ec ch hn ni ic ca al l R Re ep po or rt t 1 18 82 22 2,, R Re ev vi is se ed d M Ma ay y 1978.
[6] Shoch, J., "Inter-N Ne et tw wo or rk k N Na am mi in ng g,, A Ad dd dr re es ss si in ng g,, a an nd d R Ro ou ut ti in ng g,," "
COMPCON, IEEE Computer Society, Fall 1978.
[7] Postel, J., "Address Mappings," RFC 796,, U US SC C/ /I In nf fo or rm ma at ti io on n S Sc ci ie en nc ce es s
Institute, September 1981.
[8] Shoch, J., "Packet Fragmentation in Inter-N Ne et tw wo or rk k P Pr ro ot to oc co ol ls s,," "
Computer Networks, v. 3, n. 1, February 1979.


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