Understanding Subnetting

University of BabylonCollege of Information Technology Information Network Dept

First Class Second Semester Subject Network and Distributed System Lecture 2

Lecturer Ahmed M Al-Saleh amp Mouayad Najim Page 14

Type of addressing in IPv4

Within the address range of each IPv4 network we have three types of addresses

Network address - The address by which we refer to the network

Broadcast address - A special address used to send data to all hosts in the network

Host addresses - The addresses assigned to the end devices in the network

Network Prefixes

An important question is How do we know how many bits represent the network

portion and how many bits represent the host portion When we express an IPv4 network

address we add a prefix length to the network address The prefix length is the number of

bits in the address that gives us the network portion For example in 1721640 24 the 24

is the prefix length - it tells us that the first 24 bits are the network address This leaves the

remaining 8 bits the last octet as the host portion Later in this chapter we will learn more

about another entity that is used to specify the network portion of an IPv4 address to the

network devices It is called the subnet mask

The subnet mask consists of 32 bits just as the address does and uses 1s and 0s to indicate which

bits of the address are network bits and which bits are hosts bits

Networks are not always assigned a 24 prefix Depending on the number of hosts on

the network the prefix assigned may be different Having a different prefix number changes

the host range and broadcast address for each network

Notice that the network address could remain the same but the host range and the

broadcast address are different for the different prefix lengths In this figure you can also

see that the number of hosts that can be addressed on the network changes as well




Understanding Subnetting

Subnetting allows you to create multiple logical networks that exist within a single Class

A B or C network If you do not subnet you will only be able to use one network from your Class

A B or C network which is unrealistic

Formula for calculating subnets

Use this formula to calculate the number of subnets

2^n where n = the number of bits borrowed

The number of hosts

To calculate the number of hosts per network we use the formula of 2^n - 2

where n = the number of bits left for hosts

Each data link on a network must have a unique network ID with every node on that link

being a member of the same network If you break a major network (Class A B or C) into smaller

subnetworks it allows you to create a network of interconnecting subnetworks Each data link on

this network would then have a unique networksubnetwork ID Any device or gateway

connecting n networkssubnetworks has n distinct IP addresses one for each network subnetwork

that it interconnects




To subnet a network extend the natural mask using some of the bits from the host ID

portion of the address to create a subnetwork ID For example given a Class C network of

2041550 which has a natural mask of 2552552550 you can create subnets in this manner

2041550 - 11001100000011110000010100000000

255255255224 - 11111111111111111111111111100000

------------------------------------------------|sub|----

By extending the mask to be 255255255224 you have taken three bits (indicated by sub) from

the original host portion of the address and used them to make subnets With these three bits it is

possible to create eight subnets With the remaining five host ID bits each subnet can have up to

32 host addresses 30 of which can actually be assigned to a device since host ids of all zeros or

all ones are not allowed (it is very important to remember this) So with this in mind these subnets

have been created

2041550 255255255224 host address range 1 to 30








Note There are two ways to denote these masks First since you are using three bits more than

the natural Class C mask you can denote these addresses as having a 3-bit subnet mask Or

secondly the mask of 255255255224 can also be denoted as 27 as there are 27 bits that are set

in the mask This second method is used with CIDR Using this method one of thse networks can

be described with the notation prefixlength For example 2041553227 denotes the network

20415532 255255255224 When appropriate the prefixlength notation is used to denote the

mask throughout the rest of this document




The network subnetting scheme in this section allows for eight subnets and the network might

appear as

Figure 2

Notice that each of the routers in Figure 2 is attached to four subnetworks one subnetwork

is common to both routers Also each router has an IP address for each subnetwork to which it is

attached Each subnetwork could potentially support up to 30 host addresses

This brings up an interesting point The more host bits you use for a subnet mask the more

subnets you have available However the more subnets available the less host addresses available

per subnet For example a Class C network of 2041750 and a mask of 255255255224 (27)

allows you to have eight subnets each with 32 host addresses (30 of which could be assigned to

devices) If you use a mask of 255255255240 (28) the break down is

2041550 - 11001100000011110000010100000000

255255255240 - 11111111111111111111111111110000

--------------------------------------------------|sub |---

Since you now have four bits to make subnets with you only have four bits left for host addresses

So in this case you can have up to 16 subnets each of which can have up to 16 host addresses (14

of which can be assigned to devices)

Take a look at how a Class B network might be subnetted If you have network 1721600 then

you know that its natural mask is 25525500 or 172160016 Extending the mask to anything




beyond 25525500 means you are subnetting You can quickly see that you have the ability to

create a lot more subnets than with the Class C network If you use a mask of 2552552480 (21)

how many subnets and hosts per subnet does this allow for

1721600 - 10101100000100000000000000000000

2552552480 - 11111111111111111111100000000000

---------------------------| sub |-------------------

You are using five bits from the original host bits for subnets This will allow you to have 32

subnets (25) After using the five bits for subnetting you are left with 11 bits for host addresses

This will allow each subnet so have 2048 host addresses (211) 2046 of which could be assigned to

devices

Note In the past there were limitations to the use of a subnet 0 (all subnet bits are set to zero) and

all ones subnet (all subnet bits set to one) Some devices would not allow the use of these subnets

Cisco Systems devices will allow the use of these subnets when the ip subnet zero command is

configured

Examples

Sample Exercise 1

Now that you have an understanding of subnetting put this knowledge to use In this example you

are given two address mask combinations written with the prefixlength notation which have

been assigned to two devices Your task is to determine if these devices are on the same subnet or

different subnets You can do this by using the address and mask of each device to determine to

which subnet each address belongs

DeviceA 17216173020

DeviceB 17216281520




Determining the Subnet for DeviceA

172161730 - 10101100000100000001000100011110

2552552400 - 11111111111111111111000000000000

---------------------------| sub|---------------------

subnet = 10101100000100000001000000000000 = 17216160

Looking at the address bits that have a corresponding mask bit set to one and setting all the other

address bits to zero (this is equivalent to performing a logical AND between the mask and

address) shows you to which subnet this address belongs In this case DeviceA belongs to subnet

17216160

Determining the Subnet for DeviceB

172162815 - 10101100000100000001110000001111

2552552400 - 11111111111111111111000000000000

---------------------------| sub|------------

subnet = 10101100000100000001000000000000 = 17216160

From these determinations DeviceA and DeviceB have addresses that are part of the same subnet

Subnetting

The procedure in which we browse some Host bits from the Host portion and add it in

Network bits in Network Portion this procedure is called Subnetting In Subnetting we increase the

Network Portion and decrease the Host Portion

It means as Network Portion increases option of Sub networks also increases but the no of Hosts in each

network start to decrease

For Example

124192135159 as we know an IP address is of 32 Bits

It Is an IP address of Class A (Because in First Octet Value range is 0 ndash 126)

Its Network Portion is of 8 bits

Its Host Portion is of 24 bits

Its Subnet mask is 255000

Its Network ID is 124000




Note

IP addresses are also represented as (IPNetwork Bits)

Class A 1241921351598 In Class A Network Portion is of 8 Bits

Class B 18920019123916 In Class B Network Portion is of 16 Bits

Class C 19322016422324 In Class C Network Portion is of 24 Bits

200100100024

(IP of Class C + Network Portion = 24 Bits + Host Portion = 8 Bits)

Let us Borrow 2-Bits from Host Portion (which have Host Portion = 8-Bits)

Now Host Portion have Total Bits = 6

Add it in Network Portion (which have Network Portion = 24-Bits)

Now Network Portion have Total Bits = 26

What is Custom Sub net Mask

After Subnetting Default Subnet Mask of the IP address becomes Custom Subnet Mask

How many Subnets can form when we borrow some Bits from Host portion and add it in Network Portion

We can produce 2n (n = is equal to number of bits Borrow from Host Portion)

If we Borrow 1 Bit 2nn = 1 21

2 Subnets can form

If we Borrow 2 Bits 2nn = 2 22

4 Subnets can form


8 Subnets can form


16 Subnets can form


32 Subnets can form


64 Subnets can form




How may Maximum Bits be able to borrow from Host Portion

We can borrow maximum 6 bits from Host Portion

Note

If number of subnets increases congestion in the routing tables would be happened because size of routing

tables increases but if Bandwidth is sufficient no congestion will take place

Types of Subnetting

There are two types of Subnetting

1 Fixed Length Subnetting or Fixed Length Subnet Masking

2 Variable Length Subnetting or Variable Length Subnet Masking

1 Fixed Length Subnet Masking

If we are sure that we have limit of subnets and not increases from the limit it is called Fixed

Length Subnetting

2 Variable Length Subnet Masking

---------------------------------------------------------------------------------------------------------------------------------------

Question How Many Subnets can form using following IP Address we do sub

netting of 2-Bits and How many Hosts Can be in each subnet

2001001000

Answer Given IP address is 2001001000

1 Class C

2 Network Portion 24-Bits

3 Host Portion 08-Bits

4 Representation of IP 200100100024




5 Subnetting 2-Bits

6 After Subnetting Network Portion 26-Bits

7 After Subnetting Host Portion 06-Bits

8 After Subnetting IP 200100100026

9 Number of Subnets 2n n=2 22 4

10 Number of Hosts per Subnet 2n n=6 26 64

Default Subnet Mask

Default Subnet Mask of Class Full IP Address 200100100024

As we know to find out the Default Subnet Mask we ON all 24-Bits of Network Portion of

Class Full IP address

200 100 100 024

11111111 11111111 1111111 0

255 255 255 0

Network ID of Class Full IP 200100100024

2001001000

Custom Subnet Mask

Custom Subnet Mask of Class Less IP Address 200100100026

As we Know to find out the Custom Subnet Mask we ON all 26-Bits of Network Portion of

class Less IP Address

200 100 100 026

11111111 11111111 11111111 11000000

255 255 255 192




Subnet ID of Given Class Less IP 200100100026

200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064

Table 1 Summery of Subnetting for Class AB And C)

bits Subnet Mask CIDR Subnets Hosts

1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2




Subnetting (Dividing Networks into Right Sizes)

Every network within the internetwork of a corporation or organization is designed

to accommodate a finite number of hosts

Some networks such as point-to-point WAN links only require a maximum of two hosts Other

networks such as a user LAN in a large building or department may need to accommodate

hundreds of hosts Network administrators need to devise the internetwork addressing scheme to

accommodate the maximum number of hosts for each network The number of hosts in each

division should allow for growth in the number of hosts

Determine the Total Number of Hosts

First consider the total number of hosts required by the entire corporate internetwork

We must use a block of addresses that is large enough to accommodate all devices in all the

corporate networks This includes end user devices servers intermediate devices and router

interfaces

See Step 1 of the figure




Consider the example of a corporate internetwork that needs to accommodate 800

hosts in its four locations

Determine the Number and Size of the Networks

Next consider the number of networks and the size of each required based on

common groupings of hosts


We subnet our network to overcome issues with location size and control In

designing the addressing we consider the factors for grouping the hosts that we

discussed previously

Grouping based on common geographic location

Grouping hosts used for specific purposes

Grouping based on ownership




Each WAN link is a network We create subnets for the WAN that interconnect

different geographic locations When connecting the different locations we use a

router to account for the hardware differences between the LANs and the WAN

Although hosts in a common geographic location typically comprise a single block

of addresses we may need to subnet this block to form additional networks at each

location We need to create subnetworks at the different locations that have hosts for

common user needs We may also have other groups of users that require many

network resources or we may have many users that require their own subnetwork

Additionally we may have subnetworks for special hosts such as servers Each of

these factors needs to be considered in the network count

We also have to consider any special security or administrative ownership needs that

require additional networks

One useful tool in this address planning process is a network diagram A

diagram allows us to see the networks and make a more accurate count

To accommodate 800 hosts in the companys four locations we use binary arithmetic

to allocate a 22 block (2^10-2=1022)

Allocating Addresses

Now that we have a count of the networks and the number of hosts for each network

we need to start allocating addresses from our overall block of addresses





This process begins by allocating network addresses for locations of special

networks We start with the locations that require the most hosts and work down to

the point-to-point links This process ensures that large enough blocks of addresses

are made available to accommodate the hosts and networks for these locations

When making the divisions and assignment of available subnets make sure that there

are adequately-sized address blocks available for the larger demands Also plan carefully to

ensure that the address blocks assigned to the subnet do not overlap




In our example we now allocate blocks of addresses to the four locations as well as the WAN

links

With the major blocks allocated next we subnet any of the locations that require

dividing In our example we divide the corporate HQ into two networks




we will look at addressing from another view We will consider subnetting based on

the number of hosts including router interfaces and WAN connections This

scenario has the following requirements

bull AtlantaHQ 58 host addresses

bull PerthHQ 26 host addresses

bull SydneyHQ 10 host addresses

bull CorpusHQ 10 host addresses

bull WAN links 2 host addresses (each)

When creating an appropriate addressing scheme always begin with the largest

requirement In this case the AtlantaHQ with 58 users has the largest requirement

Starting with 192168150 we will need 6 host bits to accommodate the requirement

of 58 hosts this allows 2 additional bits for the network portion The prefix for this

network would be 26 and a subnet mask of 255255255192

Lets begin by subnetting the original address block of 192168150 24 Using the

Usable hosts = 2^n - 2 formula we calculate that 6 host bits allow 62 hosts in the

subnet The 62 hosts would meet the required 58 hosts of the AtlantaHQ company

router

Address 192168150 In Binary 11000000101010000000111100000000

Mask 25525525519226 Bits in binary 11111111111111111111111111000000




This tables shows the the Networks IP Addressing for each Corporation after using (VLSM) depeond on

the number of Hosts




Understanding Subnetting

Subnetting allows you to create multiple logical networks that exist within a single Class

A B or C network If you do not subnet you will only be able to use one network from your Class

A B or C network which is unrealistic

Formula for calculating subnets

Use this formula to calculate the number of subnets

2^n where n = the number of bits borrowed

The number of hosts

To calculate the number of hosts per network we use the formula of 2^n - 2

where n = the number of bits left for hosts

Each data link on a network must have a unique network ID with every node on that link

being a member of the same network If you break a major network (Class A B or C) into smaller

subnetworks it allows you to create a network of interconnecting subnetworks Each data link on

this network would then have a unique networksubnetwork ID Any device or gateway

connecting n networkssubnetworks has n distinct IP addresses one for each network subnetwork

that it interconnects







2041550 - 11001100000011110000010100000000

255255255224 - 11111111111111111111111111100000

------------------------------------------------|sub|----






have been created




















appear as

Figure 2









2041550 - 11001100000011110000010100000000

255255255240 - 11111111111111111111111111110000

--------------------------------------------------|sub |---












1721600 - 10101100000100000000000000000000

2552552480 - 11111111111111111111100000000000

---------------------------| sub |-------------------




devices




configured

Examples

Sample Exercise 1






DeviceA 17216173020

DeviceB 17216281520





172161730 - 10101100000100000001000100011110

2552552400 - 11111111111111111111000000000000

---------------------------| sub|---------------------

subnet = 10101100000100000001000000000000 = 17216160




17216160


172162815 - 10101100000100000001110000001111

2552552400 - 11111111111111111111000000000000

---------------------------| sub|------------

subnet = 10101100000100000001000000000000 = 17216160


Subnetting






For Example










Note





200100100024











2 Subnets can form


4 Subnets can form


8 Subnets can form


16 Subnets can form


32 Subnets can form


64 Subnets can form






Note



Types of Subnetting






Length Subnetting


---------------------------------------------------------------------------------------------------------------------------------------



2001001000


1 Class C







5 Subnetting 2-Bits






Default Subnet Mask




200 100 100 024

11111111 11111111 1111111 0

255 255 255 0


2001001000

Custom Subnet Mask




200 100 100 026

11111111 11111111 11111111 11000000

255 255 255 192





200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064



1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts







2041550 - 11001100000011110000010100000000

255255255224 - 11111111111111111111111111100000

------------------------------------------------|sub|----






have been created




















appear as

Figure 2









2041550 - 11001100000011110000010100000000

255255255240 - 11111111111111111111111111110000

--------------------------------------------------|sub |---












1721600 - 10101100000100000000000000000000

2552552480 - 11111111111111111111100000000000

---------------------------| sub |-------------------




devices




configured

Examples

Sample Exercise 1






DeviceA 17216173020

DeviceB 17216281520





172161730 - 10101100000100000001000100011110

2552552400 - 11111111111111111111000000000000

---------------------------| sub|---------------------

subnet = 10101100000100000001000000000000 = 17216160




17216160


172162815 - 10101100000100000001110000001111

2552552400 - 11111111111111111111000000000000

---------------------------| sub|------------

subnet = 10101100000100000001000000000000 = 17216160


Subnetting






For Example










Note





200100100024











2 Subnets can form


4 Subnets can form


8 Subnets can form


16 Subnets can form


32 Subnets can form


64 Subnets can form






Note



Types of Subnetting






Length Subnetting


---------------------------------------------------------------------------------------------------------------------------------------



2001001000


1 Class C







5 Subnetting 2-Bits






Default Subnet Mask




200 100 100 024

11111111 11111111 1111111 0

255 255 255 0


2001001000

Custom Subnet Mask




200 100 100 026

11111111 11111111 11111111 11000000

255 255 255 192





200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064



1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts





appear as

Figure 2









2041550 - 11001100000011110000010100000000

255255255240 - 11111111111111111111111111110000

--------------------------------------------------|sub |---












1721600 - 10101100000100000000000000000000

2552552480 - 11111111111111111111100000000000

---------------------------| sub |-------------------




devices




configured

Examples

Sample Exercise 1






DeviceA 17216173020

DeviceB 17216281520





172161730 - 10101100000100000001000100011110

2552552400 - 11111111111111111111000000000000

---------------------------| sub|---------------------

subnet = 10101100000100000001000000000000 = 17216160




17216160


172162815 - 10101100000100000001110000001111

2552552400 - 11111111111111111111000000000000

---------------------------| sub|------------

subnet = 10101100000100000001000000000000 = 17216160


Subnetting






For Example










Note





200100100024











2 Subnets can form


4 Subnets can form


8 Subnets can form


16 Subnets can form


32 Subnets can form


64 Subnets can form






Note



Types of Subnetting






Length Subnetting


---------------------------------------------------------------------------------------------------------------------------------------



2001001000


1 Class C







5 Subnetting 2-Bits






Default Subnet Mask




200 100 100 024

11111111 11111111 1111111 0

255 255 255 0


2001001000

Custom Subnet Mask




200 100 100 026

11111111 11111111 11111111 11000000

255 255 255 192





200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064



1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts







1721600 - 10101100000100000000000000000000

2552552480 - 11111111111111111111100000000000

---------------------------| sub |-------------------




devices




configured

Examples

Sample Exercise 1






DeviceA 17216173020

DeviceB 17216281520





172161730 - 10101100000100000001000100011110

2552552400 - 11111111111111111111000000000000

---------------------------| sub|---------------------

subnet = 10101100000100000001000000000000 = 17216160




17216160


172162815 - 10101100000100000001110000001111

2552552400 - 11111111111111111111000000000000

---------------------------| sub|------------

subnet = 10101100000100000001000000000000 = 17216160


Subnetting






For Example










Note





200100100024











2 Subnets can form


4 Subnets can form


8 Subnets can form


16 Subnets can form


32 Subnets can form


64 Subnets can form






Note



Types of Subnetting






Length Subnetting


---------------------------------------------------------------------------------------------------------------------------------------



2001001000


1 Class C







5 Subnetting 2-Bits






Default Subnet Mask




200 100 100 024

11111111 11111111 1111111 0

255 255 255 0


2001001000

Custom Subnet Mask




200 100 100 026

11111111 11111111 11111111 11000000

255 255 255 192





200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064



1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts





172161730 - 10101100000100000001000100011110

2552552400 - 11111111111111111111000000000000

---------------------------| sub|---------------------

subnet = 10101100000100000001000000000000 = 17216160




17216160


172162815 - 10101100000100000001110000001111

2552552400 - 11111111111111111111000000000000

---------------------------| sub|------------

subnet = 10101100000100000001000000000000 = 17216160


Subnetting






For Example










Note





200100100024











2 Subnets can form


4 Subnets can form


8 Subnets can form


16 Subnets can form


32 Subnets can form


64 Subnets can form






Note



Types of Subnetting






Length Subnetting


---------------------------------------------------------------------------------------------------------------------------------------



2001001000


1 Class C







5 Subnetting 2-Bits






Default Subnet Mask




200 100 100 024

11111111 11111111 1111111 0

255 255 255 0


2001001000

Custom Subnet Mask




200 100 100 026

11111111 11111111 11111111 11000000

255 255 255 192





200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064



1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts




Note





200100100024











2 Subnets can form


4 Subnets can form


8 Subnets can form


16 Subnets can form


32 Subnets can form


64 Subnets can form






Note



Types of Subnetting






Length Subnetting


---------------------------------------------------------------------------------------------------------------------------------------



2001001000


1 Class C







5 Subnetting 2-Bits






Default Subnet Mask




200 100 100 024

11111111 11111111 1111111 0

255 255 255 0


2001001000

Custom Subnet Mask




200 100 100 026

11111111 11111111 11111111 11000000

255 255 255 192





200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064



1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts






Note



Types of Subnetting






Length Subnetting


---------------------------------------------------------------------------------------------------------------------------------------



2001001000


1 Class C







5 Subnetting 2-Bits






Default Subnet Mask




200 100 100 024

11111111 11111111 1111111 0

255 255 255 0


2001001000

Custom Subnet Mask




200 100 100 026

11111111 11111111 11111111 11000000

255 255 255 192





200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064



1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts




5 Subnetting 2-Bits






Default Subnet Mask




200 100 100 024

11111111 11111111 1111111 0

255 255 255 0


2001001000

Custom Subnet Mask




200 100 100 026

11111111 11111111 11111111 11000000

255 255 255 192





200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064



1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts





200 100 100 65

200 100 100 01000001

255 255 255 11000000

200 100 100 01000000

200 100 100 64

2001001006526

Custom Subnet Mask

20010010065

10010010001000001

25525525511000000

255255255192

10010010001000000

20010010064



1 25512800 9 2 8388608

2 25519200 10 4 4194304

3 25522400 11 8 2097152

4 25524000 12 16 1048576

5 25524800 13 32 524288

6 25525200 14 64 262144

7 25525400 15 128 131072

8 25525500 16 256 65536

9 2552551280 17 512 32768

10 2552551920 18 1024 16384

11 2552552240 19 2048 8192

12 2552552400 20 4096 4096

13 2552552480 21 8192 2048

14 2552552520 22 16384 1024




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts




15 2552552540 23 32768 512

16 2552552550 24 65536 256

17 255255255128 25 131072 128

18 255255255192 26 262144 64

19 255255255224 27 524288 32

20 255255255240 28 1048576 16

21 255255255248 29 2097152 8

22 255255255252 30 4194304 4

23 255255255254 31 8388608 2


1 2552551280 17 2 32768

2 2552551920 18 4 16384

3 2552552240 19 8 8192

4 2552552400 20 16 4096

5 2552552480 21 32 2048

6 2552552520 22 64 1024

7 2552552540 23 128 512

8 2552552550 24 256 256

9 255255255128 25 512 128

10 255255255192 26 1024 64

11 255255255224 27 2048 32

12 255255255240 28 4096 16

13 255255255248 29 8192 8

14 255255255252 30 16384 4

15 255255255254 31 32768 2


1 255255255128 25 2 128

2 255255255192 26 4 64

3 255255255224 27 8 32

4 255255255240 28 16 16

5 255255255248 29 32 8

6 255255255252 30 64 4

7 255255255254 31 128 2
















interfaces






















































links






















router







the number of Hosts
















interfaces






















































links






















router







the number of Hosts





















































links






















router







the number of Hosts






































links






















router







the number of Hosts















links






















router







the number of Hosts





links






















router







the number of Hosts




















router







the number of Hosts





the number of Hosts

Date post:	26-Dec-2015
Category:	Documents
Upload:	sholl12
View:	87 times
Download:	6 times

Understanding Subnetting

Documents