21 - UTPA Faculty Web

cursefarmNetworking and Communications

Oct 24, 2013 (3 years and 7 months ago)

71 views

21
-
IP addressing

Dr. John P. Abraham

Professor

UTPA

Chapters 19, 20


I have already covered these concepts
elsewhere.

Addressing


Physical


Logical

IP address


32 bits


Hierarchy


prefix and suffix


Prefix identifies the network


given by IANA

In classful addressing, the network address (the
first address in the block) is the one that is
assigned to the organization. The range of
addresses can automatically be inferred from the
network address.



Suffix identifies the computer

given locally


No two computers can have the same public IP

Classful IP addressing


Divided IP address space into three
primary classes A, B, C and also there
exist class D (multicasting) and E.


First four (MSB) bits will determine its
class


Class

Lea
ding

Bits

Size of
Network

Number

Bit field

Size of
Rest

Bit
field

Number

of
Networks

Addresse
s

per
Network

Start
addres
s

End
address

Class A


0


8


24


128
(2
7
)


16,777,
216 (2
24
)

0.0.0.0

127.255.
255.255

Class B


01


16


16


16,384
(2
14
)


65,536
(2
16
)

128.0.0.
0

191.255.
255.255

Class C


110


24


8


2,097,1
52 (2
21
)


256 (2
8
)

192.0.0.
0

223.255.
255.255

Class D
(
multicast
)

1110


not
defined


not
defined


not
defined


not
defined

224.0.0.
0

239.255.
255.255

Class E
(reserved)

1111


not
defined


not
defined


not
defined


not
defined

240.0.0.
0

255.255.
255.255


Finding the address class

Figure 4.5

Finding the class in decimal notation

Find

the

class

of

each

address
:

a
.

227
.
12
.
14
.
87

b
.
193
.
14
.
56
.
22

c
.
14
.
23
.
120
.
8

d
.

252
.
5
.
15
.
111

e
.
134
.
11
.
78
.
56

Solution

a
.

The

first

byte

is

227

(between

224

and

239
)
;

the

class

is

D
.

b
.

The

first

byte

is

193

(between

192

and

223
)
;

the

class

is

C
.

c
.

The

first

byte

is

14

(between

0

and

127
)
;

the

class

is

A
.

d
.

The

first

byte

is

252

(between

240

and

255
)
;

the

class

is

E
.

e
.

The

first

byte

is

134

(between

128

and

191
)
;

the

class

is

B
.

Subnet Addressing







The network address is the beginning
address of each block. It can be found by
applying the default mask to any of the
addresses in the block (including itself). It
retains the netid of the block and sets the
hostid to zero.

Given

the

address

23
.
56
.
7
.
91
,

find

the

beginning

address

(network

address)
.

Example

12

Solution

The

default

mask

is

255
.
0
.
0
.
0
,

which

means

that

only

the

first

byte

is

preserved

and

the

other

3

bytes

are

set

to

0
s
.

The

network

address

is

23
.
0
.
0
.
0
.

What

is

the

subnetwork

address

if

the

destination

address

is

200
.
45
.
34
.
56

and

the

subnet

mask

is

255
.
255
.
240
.
0
?

Example

15

Solution

We apply the AND operation on the address and the subnet
mask.

Address





11001000 00101101 00100010 00111000

Subnet Mask




11111111 11111111 11110000 00000000

卵b湥n睯rk 䅤dr敳s


11001000 00101101 00100000 00000000.

Figure 4.25

Comparison of a default mask and a subnet mask

Table 4.3 Special addresses

Private IPs

CIDR notation


Classless Inter
-
Domain routing (CIDR)


CIDR


CIDR is an alternative to traditional

IP
subnetting
that organizes IP addresses
into subnetworks independent of the value
of the addresses themselves. CIDR is also
known as

supernetting

as it effectively
allows multiple subnets to be grouped
together for network routing.


Ddd.ddd.ddd.ddd/m 192.5.48.69/26


CIDR


Prefix length is given after the slash


230.8.24.56/16 gives block of 230.8.0.0 to 230.8.255.255


To find the first address AND the mask.


To find the last address, find the complement of the mask, then OR.

CIDR example


One of the address in a block is 17.63.110.114/24. Find the number
of address, the first address, and the last address of the block.

17

63 110 114

255

255 255 0 AND

17 63 110 0 IS THE FIRST ADDRESS

---

17

63 110 114

0 0 0 255 OR

17
63 110 255 IS THE LAST ADDRESS

CIDR example


110.23.120.14.20. Find the first and last
address

110

23 120 14

255

255 240 0 AND

110

23 112 0


110 23 120 14

0 0 15 255 OR

110

23 127 255 LAST ADDRESS