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The Target Audience Is Anyone Who Desires A Practical And Technical Introduction To The Field Of Networking. This Includes High School, Community College, And Lifelong-Learning Students Who Are Interested In Careers As Network Technicians, Network Engineers, Network Administrators, And Network Help-Desk Staff.

NOTE: THIS CALCULATOR REQUIRES THE USE OF JAVASCRIPT ENABLED AND CAPABLE BROWSERS. THE FOLLOWING UTILITY CALCULATES THE NETWORK AND BROADCAST ADDRESSES THAT A GIVEN IP ADDRESS IS ASSOCIATED WITH. THE CALCULATIONS ARE BASED ON RFC 1219 COMPLIANT ADDRESSES.

Plz Note:

Some Topics That You Might Want To Pursue On Your Own That We Did Not Cover In This Article Are Listed Here. This Page Discusses “IP SUBNETTING CALCULATOR (ALL IN ONE):”, And Also We Request To The Students, Please Go Through All The Articles That Are We Posted In This Web Site And Also Identify All The CISCO IOS Commands In The Lab Practice Before Going To Access This Page. Experience Is The Sequence Of Hands-On LABs.Thank You!

FOR MORE REFERENCES:

◙ - ➤ For More Reference - > IP ADDRESSING AND SUBNETTING:

◙ - ➤ For More Reference - > SUBNETTING TUTORIAL

◙ - ➤ For More Reference - > IP SUBNETTING STEP BY STEP EXAMPLES:

◙ - ➤ For More Reference - > VARIABLE LENGTH SUBNET MASK (VLSM):

◙ - ➤ For More Reference - > BASIC – IP CLASSFUL Vs IP CLASSLESS:

◙ - ➤ For More Reference - > IPv4 & IPv6:

◙ - ➤ For More Reference - > CONVERTING FROM IPv4 TO IPv6:

◙ - ➤ For More Reference - > BASIC COLLECTION OF NETWORKING CONCEPTS:

◙ - ➤ For More Reference - > BASIC NETWORKING QUESTIONS AND ANSWER:

◙ - ➤ For More Reference- > IP ROUTING QUESTIONS AND ANSWERS:

IP ADDRESS SUBNETTING

IP ADDRESS SUBNETTING:

An IP (Internet Protocol) Address Is A Unique Identifier For A Node Or Host Connection On An Ip Network. An Ip Address Is A 32 Bit Binary Number Usually Represented As 4 Decimal Values, Each Representing 8 Bits, In The Range 0 To 255 (Known As Octets) Separated By Decimal Points. This Is Known As "Dotted Decimal" Notation.

EXAMPLE: 140.179.220.200

TO VIEW THE VALUES IN THEIR BINARY FORM:

140 . 179 . 220 . 200
10001100.10110011.11011100.11001000

Every IP Address Consists Of Two Parts, One Identifying The Network And One Identifying The Node. The Class Of The Address And The Subnet Mask Determine Which Part Belongs To The Network Address And Which Part Belongs To The Node Address.

ADDRESS CLASSES:

There Are 5 Different Address Classes. You Can Determine Which Class Any Ip Address Is In By Examining The First 4 Bits Of The IP Address.

CLASS A Addresses Begin With 0xxx, Or 1 To 126 Decimal.
CLASS B Addresses Begin With 10xx, Or 128 To 191 Decimal.
CLASS C Addresses Begin With 110x, Or 192 To 223 Decimal.
CLASS D Addresses Begin With 1110, Or 224 To 239 Decimal.
CLASS E Addresses Begin With 1111, Or 240 To 254 Decimal.

Addresses Beginning With 01111111, Or 127 Decimal, Are Reserved For Loopback And For Internal Testing On A Local Machine (You Should Always Be Able To Ping 127.0.0.1, Which Points To Yourself). Class D Addresses Are Reserved For Multicasting; Class E Addresses Are Reserved For Future Use. They Should Not Be Used For Host Addresses.

IN THE EXAMPLE: 140.179.220.200 Is A Class B Address So By Default The Network Part Of The Address (Also Known As The Network Address) Is Defined By The First Two Octets (140.179.X.X) And The Node Part Is Defined By The Last 2 Octets (X.X.220.200).

In Order To Specify The Network Address For A Given Ip Address, The Node Section Is Set To All "0"S. In Our Example, 140.179.0.0 Specifies The Network Address For 140.179.220.200. When The Node Section Is Set To All "1"S, It Specifies A Broadcast That Is Sent To All Hosts On The Network. 140.179.255.255 Specifies The Example Broadcast Address. Note That This Is True Regardless Of The Length Of The Node Section.

SUBNETTING:

SUBNETTING An IP Network Can Be Done For A Variety Of Reasons, Including Organization, Use Of Different Physical Media (Such As Ethernet, Fddi, Wan, Etc.), Preservation Of Address Space, And Security. The Most Common Reason Is To Control Network Traffic. In An Ethernet Network, All Nodes On A Segment See All The Packets Transmitted By All The Other Nodes On That Segment. Performance Can Be Adversely Affected Under Heavy Traffic Loads, Due To Collisions And The Resulting Retransmissions. A Router Is Used To Connect Ip Networks To Minimize The Amount Of Traffic Each Segment Must Receive.

PRIVATE SUBNETTING:

There Are Three IP Network Addresses Reserved For Private Networks. The Addresses Are 10.0.0.0, Subnet Mask 255.0.0.0, 172.16.0.0, Subnet Mask 255.240.0.0, And 192.168.0.0, Subnet Mask 255.255.0.0. These Addresses Are Also Notated 10.0.0.0/8, 172.16.0.0/12, And 192.168.0.0/16; They Can Be Used By Anyone Setting Up Internal Ip Networks, Such As A Lab Or Home Lan Behind A Nat Or Proxy Server Or A Router. It Is Always Safe To Use These Because Routers On The Internet By Default Will Never Forward Packets Coming From These Addresses. These Addresses Are Defined In RFC 1918.

SUBNET MASKING:

Applying A Subnet Mask To An IP Address Allows You To Identify The Network And Node Parts Of The Address. The Network Bits Are Represented By The 1s In The Mask, And The Node Bits Are Represented By The 0s. Performing A Bitwise Logical And Operation Between The IP Address And The Subnet Mask Results In The Network Address Or Number.

FOR EXAMPLE, Using Our Test IP Address And The Default Class B Subnet Mask, We Get:

10001100.10110011.11110000.11001000 140.179.240.200 Class B IP Address
11111111.11111111.00000000.00000000 255.255.000.000 Default Class B Subnet Mask
-------------------------------------------------------------------
10001100.10110011.00000000.00000000 140.179.000.000 Network Address

DEFAULT SUBNET MASKS:

Class A - 255.0.0.0 - 11111111.00000000.00000000.00000000
Class B - 255.255.0.0 - 11111111.11111111.00000000.00000000
Class C - 255.255.255.0 - 11111111.11111111.11111111.00000000

Additional Bits Can Be Added To The Default Subnet Mask For A Given Class To Further Subnet, Or Break Down, A Network. When A Bitwise Logical And Operation Is Performed Between The Subnet Mask And Ip Address, The Result Defines The Subnet Address (Also Called The Network Address Or Network Number). There Are Some Restrictions On The Subnet Address. Node Addresses Of All "0"S And All "1"S Are Reserved For Specifying The Local Network (When A Host Does Not Know Its Network Address) And All Hosts On The Network (Broadcast Address), Respectively.

This Also Applies To Subnets. A Subnet Address Cannot Be All "0"S Or All "1"S. This Also Implies That A 1 Bit Subnet Mask Is Not Allowed. This Restriction Is Required Because Older Standards Enforced This Restriction. Recent Standards That Allow Use Of These Subnets Have Superseded These Standards, But Many "Legacy" Devices Do Not Support The Newer Standards. If You Are Operating In A Controlled Environment, Such As A Lab, You Can Safely Use These Restricted Subnets.

TO CALCULATE THE NUMBER OF SUBNETS OR NODES: Use The Formula (2n-2) Where N = Number Of Bits In Either Field, And 2n Represents 2 Raised To The Nth Power. Multiplying The Number Of Subnets By The Number Of Nodes Available Per Subnet Gives You The Total Number Of Nodes Available For Your Class And Subnet Mask. Also, Note That Although Subnet Masks With Non-Contiguous Mask Bits Are Allowed, They Are Not Recommended.

EXAMPLE:

10001100.10110011.11011100.11001000 140.179.220.200 IP ADDRESS
11111111.11111111.11100000.00000000 255.255.224.000 SUBNET MASK
-------------------------------------------------------------------
10001100.10110011.11000000.00000000 140.179.192.000 SUBNET ADDRESS
10001100.10110011.11011111.11111111 140.179.223.255 BROADCAST ADDRESS

IN THIS EXAMPLE: A 3 Bit Subnet Mask Was Used. There Are 6 (23-2) Subnets Available With This Size Mask (Remember That Subnets With All 0's And All 1's Are Not Allowed). Each Subnet Has 8190 (213-2) Nodes. Each Subnet Can Have Nodes Assigned To Any Address Between The Subnet Address And The Broadcast Address. This Gives A Total Of 49,140 Nodes For The Entire Class B Address Subnetted This Way. Notice That This Is Less Than The 65,534 Nodes An Unsubnetted Class B Address Would Have.

You Can Calculate The Subnet Address By Performing A Bitwise Logical And Operation Between The Ip Address And The Subnet Mask, Then Setting All The Host Bits To 0s. Similarly, You Can Calculate The Broadcast Address For A Subnet By Performing The Same Logical And Between The Ip Address And The Subnet Mask, Then Setting All The Host Bits To 1s. That Is How These Numbers Are Derived In The Example Above.

SUBNETTING Always Reduces The Number Of Possible Nodes For A Given Network.

FORMULA FOR DEFINING A SUBNET MASK:

1. Determine The Class And The Default Subnet Mask Of The IP Address You Have Been Given.
2. Identify The Number Of Subnetworks (Subnets) That Are Required.
3. Determine How Many Bits Are Required To Support The Total Number Of Subnets.
4. Starting From The Left Hand Side Of The Binary Chart, Count Out The Number Of Bits Required To Support The Subnet Mask.
5. The Value Under The Last Bit That You Counted Is The Subnet Mask Value That Will Support The Required Number Of Subnets.
6. The Remaining Bits To The Right Hand Side Of The Subnet Mask Will Be Used To Represent The Host Portion Of The IP Address.

EXAMPLE: YOU HAVE AN IP ADDRESS OF 138.45.0.0 WHICH YOU NEED TO SUBNETWORK INTO 45 INDIVIDUAL NETWORKS.

STEP 1: Determine The Class And The Default Subnet Mask Of The IP Address You Have Been Given. IP Address 138.45.0.0 Is A Class B Address With A Default Subnet Mask Of 255.255.0.0

STEP 2: Identify The Number Of Subnetworks (Subnets) That Are Required. 45 Individual Networks (Subnets) Will Be Required.

STEP 3: Determine How Many Bits Are Required To Support The Total Number Of Subnets.

You Can Determine This By Figuring The Binary Value Of 45 Which Is 00101101. This Tells Us That It Takes A Total Of 6 Bits To Support The Value Of 45, 101101.

* The Fastest Way To Figure The Number Of Bits Required Is To Use The IP Address CHEAT CHART. (Remember To Subtract 1 From The Possible # Of Hosts Or Subnets Section).

STEP 4: Starting From The Left Hand Side Of The Binary Chart, Count Out The Number Of Bits Required To Support The Subnet Mask.

STEP 5: To Determine The Subnet Mask Value, Perform A Binary To Decimal Conversion On Your Previous Result Or Use The IP Cheat Chart.

ANSWER: To Support 45 Individual Networks With A Given Network ID Of 138.45.0.0 We Would Have To Use A Subnet Mask Of 255.255.252.0

IN ADDITION: Given The Subnet Mask Of 255.255.252.0, How Many Host Addresses Could You Support Per Each Subnetwork?

Answer: To Solve This Question, You Will Simply Determine The Number Of Bits That Are In The Host Portion Of The IP Address. Since There Are 10 Bits Remaining In The Host ID Portion Of The IP Address, You Would Take 2 10 Which Is 1,024 - 2 (For The Invalid Addresses) = 1,022 Total Hosts Per Subnetwork.

STEPS FOR DETERMINING ALL VALID NETWORK ID’S:

1. Calculate The Binary Value Of The Octet That Will Be Used To Determine The Subnet.
2. Determine The Decimal Value Of The Smallest Bit Used In The Subnet Mask. This Value Becomes The Incremental Value.
3. List The Subnet Octet In Binary (Low Order) And Convert The Binary Value Into A Decimal Value Subtracting 1 From The Result. This Will Give You The Total Number Of Subnets Available.
4. List Each Subnet Address Starting With The Incremental Value Determined In Step 2 And Increasing By That Value Until The Total Number Of Available Subnets Is Reached.

EXAMPLE: Given Our Previous IP Address Of 138.45.0.0 With A Subnet Mask Of 255.255.252.0, Determine All Valid Network ID’s.

REFER TO THE FIGURE BELOW FOR EACH STEP:

STEP 1: Calculate The Binary Value Of The Octet That Will Be Used To Determine The Subnet.

The Third Octet Will Determine Which Part Of The IP Address Will Represent The Network ID As Opposed To The Host ID In Our Example. Therefore 252 = 11111100 In Binary.

STEP 2: Determine The Decimal Value Of The Smallest Bit Used In The Subnet Mask. This Value Becomes The Incremental Value.

The Decimal Value Of The Smallest Bit Used Is 4, So 4 Will Be The First Available Subnetwork Address With Each Address That Follows Increasing By Increments Of 4.

STEP 3: List The Subnet Octet In Binary (Low Order) And Convert The Binary Value Into A Decimal Value Subtracting 1 From The Result. This Will Give You The Total Number Of Subnets Available.

The Decimal Value Of The Binary Address Listed In Low Order Is 63. 63 - 1 = 62, Therefore 62 Is The Total Number Of Valid Network ID’s.

STEP 4: List Each Subnet Address Starting With The Incremental Value Determined In Step 2 And Increasing By That Value Until The Total Number Of Available Subnets Is Reached.

Since The Incremental Value In Our Exercise Is 4, The First Available Subnet Address Will Be 138.45.4.0 Followed By 138.45.8.0 And So On.

DETERMINING VALID HOST ID’S STEP 1, Starting With The First Valid Network ID Range, List The Smallest (1) Up To The Largest (254) Host ID’s. (The Following Graphic Uses The IP Address And Subnet Mask From The Previous Exercise)

IP ADDRESS I.E. 131.45.168.4: The 32-Bit Number That Identifies An Individual Device Such As A PC, Router, Or Printer. Each IP Address Must Be Unique To All Other IP Addresses On The Network.