Chapter 5-Subnetting-Supernetting and Classless Addressing

Chapter 5 Subnetting/Supernetting and Classless Addressing

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Outline o

Subnetting

o

Supernernetting

o

Classless addressing





















5.1

SUBNETTING





















Subnetting o

IP addresses are designed with two level of hierarchy n

o

Two levels of hierarchy is not enough

Solution: subnetting n

A network is divided into several smaller





















I P addr esses ar e des desi gne gn ed wi th two lle evel vel s of hi ar chy. h i er archy.





















Figure 5-1

A N etwor twork k wi with th T wo L evel s of H i er ar arc ch y (n (not ot Su bne bnette tted) d)























Figure 5-2

A N etwor twork k wi with th T h r ee L eve vell s of H i er ar archy chy (Su (Su bne bnette tted) d)























Subn Su bnet etti ting ng (Co Cont nt.) .) o

The subnetw subnetworks orks still appear as a single single























Three Levels of Hierarchy o

Three level























Figure 5-3

A ddr ddre esses i n a Ne N etwor k wi with th and wi wi th tho ou t Su Su bne bnetti ttin n g























Subnet Mask o

The network mask create the network address



































































































































































































































































































































































































Solution o

o

The number of 1s in the default def ault mask is 16 (class B). The company needs 1000 subnets. n n

o

This number 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.





















Soluti olu tion on (Conti (Conti nue nu ed) o

o

The mask is 11111 11 11111 111 1 11 1111 11111 1111 1 111 11111 1111 111 1 11 11000000 000000 or 255.255.255.192. 255.255 .255.192. The number of subnets is 1024.





















Figure 5-9

E x ampl mple e 4





















Variable Length Subnetting o

A site that is granted a class C address and have five subnets with the number of hosts n

o

60, 60, 60, 30, 30

Cannot use a subnet mask with only extra 2 bits





















Variab Var iable le Lengt Length h Subnett Subnetting ing (Co (Cont.) nt.) o

Solution n

o

Variable length subnetting

Use two different masks, one applied after af ter the other n

First use the mask with 26 1s (255.255.255.192) to divide the network into four into four subnet subnet























Figure 5-10

V ar arii able ble-L -L ength Subn Subne etti ttin n g























5.2























Supernetting o

Class A and B addresses are almost depleted.























Figure 5-11

A Su pe perr n etwor twork k























Make a Supernet o

Rules



































































































































































































































































































































































































Slash Notation o

Attach the number of 1s in a mask to mask to the end of a classless address

o

Also called CIDR (C (C lassless I lassless I nter nter Domain D omain R Routing) outing)

o

The CIDR convey two ideas n

The address is classless

n

Routing is done using interdom interdomain ain routing routing





















Figure 5-14

Sl as ash h N ota otati ti on





















Sl ash ash n otation otati on i s als al so cal ca l l ed call CIDR notation.





















Prefix and Suffix o

Prefix n

o

Prefix range: the length of the prefix n

o

Another name for the common part of the address range Equal to n in the slash notation

Suffix n

The varying part of the address range





















E xampl e 11 x ample

A small organization is given a block with the beginning address and the prefix length 205.16.37.24/29 (in slash notation). What is the range of the block?























Solution o

The beginning address is 205.16.37.24.























E xampl e 12 xample We can find the range of addresses in Example 11 by























A bloc bl ock k i n clas cl ass ses A , B, B , and C























Finding the Network Address o

We can derive the network address if we know























E xample xampl e 13 13 What is the network address if one of the addresses is































































































































































































































Chapter 5-Subnetting-Supernetting and Classless Addressing

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