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2
Subnetting
Objetivo: Compartir una direccin de red IP entre variasredes fsicas
Beneficios Uso eficiente de direcciones IP (referido a no desperdiciar
direcciones)
Salvar limitaciones de hardware (distintos tipos de red,cantidad mxima de nodos soportados, distancia)
Divisin en subredes de acuerdo a la estructura de laorganizacin
Caractersticas Agregado de un nivel jerrquico en la direccin IP Invisible para los routers externos Implementacin a travs de mscaras de subred
Mejoras
Restriccin en el uso de mscaras para facilitar laadministracion al crecer la red (flexibilidad)
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Basic Addressing
10.1.1.1
IP addresses are written
in dotted decimal
format.
Four sections are
separated by dots.
Each section contains a
number between 0 and255.
Dots separate the sections
Each section
contains a number
between 0 and 255
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4
Direcciones IP
Clase
A
B
C
D
E
8 16 240 32
0 RED HOST HOST HOST
HOST HOST
HOSTRED RED
RED10
110
1110
11110
RED
RED
ID GRUPO
MULTICAST
E X P E R I M E N T A L
0.0.0.0 a 127.255.255.255
128.0.0.0 a 191.255.255.255
192.0.0.0 a 223.255.255.255
224.0.0.0 a 239.255.255.255
240.0.0.0 a 247.255.255.255
Formato Rango Redes/Hosts
126/16.777.214
16.382/65.534
2.097.150/254
Direccin especial: loopbak (127.0.0.0):
* Para comunicaciones de procesos en la misma mquina.
* Nunca es propagada a la red
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5
Direcciones IP Privadas
Direcciones privadas
10.0.0.0 a 10.255.255.255 (una clase A)
172.16.0.0 a 172.31.255.255 (16 clasesB)
192.168.0.0 a 192.168.255.255 (255
clases C)
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6
Subnetting: uso de mscaras
Mscara de subred
Utilizada para indicar cules bits de una direccin IP
corresponden a red y cules a host
Nmero de 32 bits, expresado en notacin decimal con
puntos, como una direccin IP
Los bits en 1 de la mscara indican que los
correspondientes bits de una direccin IP conforman la
direccin de red, los bits en 0 indican host
El router tendr en cuenta la mscara de subred para
tomar las decisiones de ruteo.
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Mascara por default
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Example 1
What is the subnetwork address if thedestination address is 200.45.34.56 and the
subnet mask is 255.255.240.0?
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Solution
11001000 00101101 00100010 0011100011111111 11111111 11110000 00000000
11001000 00101101 00100000 00000000
The subnetwork address is 200.45.32.0.
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Example 2
What is the subnetwork address if thedestination address is 19.30.80.5 and the
mask is 255.255.192.0?
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Figure 5-6
Example 2
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Figure 5-7
Comparison of a default mask and
a subnet mask
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Example 3
A company is granted the site address201.70.64.0 (class C). The company needs
six subnets. Design the subnets.
Solution
The number of 1s in the defaultmask is 24 (class C).
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Solution (Continued)
The company needs six subnets. This number6 is not a power of 2. The next number that is
a power of 2 is 8 (23). We need 3 more 1s in
the subnet mask. The total number of 1s inthe subnet mask is 27 (24 +3).
The total number of 0s is 5 (32-
27). Themask is
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Solution (Continued)
11111111 11111111 11111111 11100000or
255.255.255.224The number of subnets is 8.
The number of addresses in each subnet
is 25(5 is the number of 0s) or 32.
Fi 5 8
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Figure 5-8
Example 3
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Example 4
A company is granted the site address181.56.0.0 (class B). The company needs
1000 subnets. Design the subnets.
Solution
The number of 1s in the default mask is 16(class B).
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Solution (Continued)
The company needs 1000 subnets. Thisnumber is not a power of 2. The next number
that is a power of 2 is 1024 (210). We need 10
more 1s in the subnet mask.The total number of 1s in the subnet mask is
26 (16 +10).
The total number of 0s is 6 (32 -26).
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Solution (Continued)
The mask is11111111 11111111 11111111 11000000
or
255.255.255.192.
The number of subnets is 1024.
The number of addresses in each subnet is 26(6 is the number of 0s) or 64.
Figure 5 9
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Figure 5-9
Example 4
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Llenar el siguiente cuadro
Subred N1 Id de subred Rango de host Id de broadcast
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Ejercicio 2
Para la direccin 172.16.10.0
Y requieres establecer 36 subredes
Encuentre el rango de direcciones de la quinta red .
Y puedo tener 70 subredes con esta direccin?
