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Tuesday, December 5, 2017

21 Indian Railways, IRCTC Tips and Tricks To Make Your Train Journey Easier and Safer in India

Hello, I’m Sujoy and today I’ll share some train travel hacks / tricks which I learned during my travels by trains.

1.    Getting Confirmed Ticket_Trick 1
When ticket between two stations is not available, try booking one or two stations back. Since every station has it’s own quota, you can easily get ticket this way! See below screenshot, I wanted to travel from BWN to DHN, but there's waiting list of 2. However, when I given previous station in train's route, that is BDC, it's showing available 69. This can save your life one day!
2.    Getting Confirmed Ticket_Trick 2
When ticket between two stations is not available, try break journey ticketing. See screenshot below. Ticket between KALKA and HOWRAH showing not available. But when I search for KALKA to DELHI, ticket available, then DELHI to HOWRAH again available in same train! This way I got confirmed ticket!

3. Current Reservation-
You know about current reservation, right? There are two types of reservations in railways, first is pre-chart reservation, that is reserving your seat before the reservation chart is prepared (which you see pasted beside each reserved coach door). Second type of reservation is post-chart reservation, also called ‘current reservation’. Most popular railway stations have a reservation counter named- ‘current reservation’. From where you can reserve your seats before 1hr of actual departure of train.
Now this facility has come online too! For some stations and for selected trains, you can book ‘current reservation’ tickets online. Just look for curr_avl writing while making online reservations via IRCTC. It's handy for booking tickets for next day journey! See screenshot below.
4. Multi-Voltage Charger-
Many long-distance trains have plug points to charge your mobile, laptop etc. But all chargers/adapters will not work! The output voltage is 110v AC (normal household voltage is 220V AC), so carry a charger/adapter which supports wide voltage, my mobile charger supports AC range 110v-350v.

5. How to Find Your Seat Easily?
Outside of every coach, near the door there's a number pair, which tells you how many seats are there in the coach and in what order. Look at below picture, the arrow mark indicates the sequence of the seat. For example- if it says 1-73>, it means there are 73 seats, and if you enter through this door, you’ll get seats starting from number 1. Similarly, 73-1> means if you enter through this door, you’ll get seats starting from number 73. Look at the picture below.


6. Know Anything About Any Train and Any Station Online-
You can search trains and can know everything about the train you are about to travel in using the website www.indiarailinfo.com .See screenshot below, click on it to see larger picture.

To know it’s complete features, watch my YouTube video. https://youtu.be/oKTThl_fd8g


7. User Smart-Cards-
Use Smart Card of your zone’s railway and metro. They have many benefits, first, you don’t have to stand in the queue every day to get tickets. Second, they give up to 10% extra balance per recharge, like 110 balance in 100 recharge! You can also use CoTVM (cash operated ticket vending machines), they accept both cash and cards for ticket dispensing. You can recharge your smart cards from ATVMs also, no need to stand in the queue again!

8. National Train Enquiry System (NTES)-
Just download the National Train Enquiry System (NTES) app and there you can track a train LIVE, check delayed or cancelled trains, live status of any platform, trains between stations, rescheduled and diverted trains; everything with last to the minutes updates. You can use the web version of the service here- https://enquiry.indianrail.gov.in/

9. Use Unreserved Ticketing System (UTS) App-
It’s an revolutionary app! It lets you buy unreserved ticket from nearby station without physically going to railway ticket counter. You can even get platform ticket in the app! It can save your money & time.
One day I was travelling from Asansol to Howrah in evening's train, with expected time at howrah 21:20. But due to severe rain, train was running 1hr late. Getting a local bus from Howrah at that time was risky. So I decided to enter Kolkata by Sealdah route by getting down to Bandel. But I had ticket for Howrah route only! I immediately booked unreserved ticket in UTS app for Bandel to Sealdah for local train!

10. Prediction of Getting Confirmed Ticket!
 Use 'TrainMan' app, to know your chances of getting confirmed ticket on a particular train, on a particular date! Below screenshot shows % chances of getting confirmed ticket in KALKA MAIL for next 7 days!

11. Use Official IRCTC Rail Connect App-
If you're always on the move, then IRCTC's RailConnect app needs no introduction to you, you can book train tickets, book flights at discount rates, book your meal in train all in one app.


12. Consider Railway Retiring Rooms, Save Money!
If you are travelling on a budget, you can consider Indian Railways retiring rooms, available at most big stations and tourist destinations. You can get a Double-Bed Non-AC Room at just 250/- and Double-Bed AC Room at just 400/- per day! Trust me, they're best value for money. You just need to have a valid ticket to avail the service. You can now book them online also from IRCTC tourism website.

13. Carry Medical Kit With You-
I always carry this Small Medical Emergency Kit in my bag. It contains- Sterilized Gauze, Cotton Swabs, Band-Aids, Amrutanjan Balm (headache, cold, and muscle pain), Borolin (antiseptic moisturizer cream), Safety pin and new blade. With medicines like- Paracetamol (for Fever/Headache/Toothache, minor pain), O2 (for dysentery/loose motion), Cheston Cold (for small cold), Gelusil Tab (antacid), Pepfiz (antacid and antiflatulant), Domstol (anti-vomiting & nausea), Stop AlerG 10mg (for anti-allergies). It can save your life!

 14. Carry Aadhaar Card With You-
Carry your Aadhar Card instead of Driving License/PAN/Voter card. And keep a scan copy in your mail/Dropbox/Google Drive. If you lost your wallet, you can simply lodge an FIR and print a color copy of your Aadhar Card, laminate it in card size, and it’s equally valid as your original Aadhar Card.
Which is not in case with Voter/PAN/Driving License. If those cards are lost, you’ve to bear lots of pain getting duplicate copy. Specially if you work outside your home town.

15. Carry Your MediClaim Card With You-
Always carry your health insurance policy card in your wallet with your Blood Group and Emergency Contact Numbers written on it. If you have some medical complications or medical restrictions, also mention that. It’s extremely important because if you ever get senseless and needed to be admitted to a hospital and needed surgery or blood transfer, that can save precious time detecting your blood group. Also, your family can be informed on the emergency contact numbers.

16.  Luggage Safety-
It's very important to carry lock & chain if you've extra luggage with you. Whether you keep it beneath your seat, or place it in overhead rack, don't forget to lock it with your seat/lluggage rack with chain. Also carry a small padlock and lock main compartment of your rucksack.

17. Carry IRCTC Menu Card With You and Never Pay Extra!
Do you know in Railways, every food item has fixed price? We generally don't ask for menu card while ordering food in train, but we should. Watch this video-
https://www.youtube.com/watch?v=dUPo9L_vwcs

Carry IRCTC Menu Rate List PDF file with you and never ever pay extra for your meal from next time. Download from given link www.swr.indianrailways.gov.in/uploads/files/1406784522498-MenuMeals.pdf


 18. Odd-Even Formula!
It’s simple! Up trains have odd train number, and come to odd numbered platform; down trains have even train number and come to even numbered platform.
For example- The ‘Up’ Rajdhani Express (heading towards Delhi) has train number 12305 and comes to platform 9 at Howrah. Similarly, Delhi-Howrah “Down” Rajdhani Express has train number 12306 and comes to platform 14 at Delhi. However, the platform rule can have exceptions depending on the congestion on station and platform.

 19. Up-Down Rule-
In previous paragraph, I mentioned ‘Up’ and 'Down' Rajdhani Express. But do you know what they exactly mean? Well, they refer to altitude difference of Starting and Ending stations.
For example, the altitude of New Delhi station is 216m, whereas altitude of Howrah station is 10m, from sea level. So, New Delhi is situated at upper altitude, so when a train is going to New Delhi from Howrah, the train will be ‘Up’ train, and train number will be ‘Odd Number’. Simple!
There is another logic, trains coming to headquarters, base station, are called ‘down’ trains.

 20. Carry a Backup Phone-
Even you've a fancy iPhone or shiny Mi-Mix 2 with you as your main device, if you're on a long distance journey, it's advised to have a backup phone with BSNL/AirTel sim card in it, as they have PAN India network coverage.

 21. Wake-Up Alarm Service!
 If you’ve ever missed your station because you'd fall asleep, then this service is for you! Just SMS ALERT <PNR NUMBER> to 139. Example-  ALERT 1234567890 and send it to 139. You’ll get a wakeup call from Indian Railways 30 minutes before your scheduled arrival at your station on your registered mobile number.
This service is not full-proof for many reasons, you may not have signal in your phone at that time, your train can be late. Moreover, this service is chargeable at 3/- per SMS. Better, what I personally do is, to put an alarm on my mobile 20 minutes before expected arrival (checked by NTES) at my destination station.

So these were my 21 IRCTC Indian Railways Tips that I learned during my travels by trains in India. Hope to learn some more in future! Let me know how you like my article,comment below if you know some more tricks. Share it with everyone you know to make their life easier, sharing is caring!

Sunday, April 9, 2017

Induction Cooktops vs LPG Gas, Which is More Economical in India? My Experience with CESC Kolkata

Hello friends, I’m Sujoy from India. Today I’ll answer the question which might also be coming in your mind, which is most economical medium of cooking, LPG Gas Oven or Induction Cooktop?

Before I begin, let me tell you about myself, we’re a typical Bengali family of two. Induction was our main cooking medium for everything since morning to night for last 3 years. With around 1hr of usage per session of cooking.

I have used Prestige 1900-watt Induction Cooktop for 2 years, which underwent many repairs, but still served me! Let me tell you some facts about it. I mostly used it on 1100-watt rating with 1300-watt for rice, and 1500-watt for Roti. It used to cook fast during initial dayslater as it aged, it started to give lesser heat per wattage. And mainly the micro switches on control panel went faulty every one or two months. But it did not show any major problem during 1st year warranty period except micro switches.


In second year, I had to change whole control board once from 3rd party repair shop. During warranty period, service center (yes there’s no home service for Prestige) took 1-2 week to repair it, due to heavy workload as they repair all kind of Prestige products in the same service center. You can watch my video on that Induction here- Life Hack #6: 5 Tips to use Induction Cooktops or Induction Cookers.

Later I bought Crompton Greaves ACGIC-CREST 1500-watt induction cooktop. It was small and compact and consumed much less energy, I used it mostly on 900-1100-watt scale, never needed to use above that as energy output was good. I stopped preparing Roti on induction although. I used it for 1 year and 1 month. However, in the 2nd month itself, I needed to replace the micro-switches. It underwent 4 repairs, including replacement of control panel board in 3rd and power circuit board in 4th repair, within one year warranty period. The only consolation is that Crompton has free home service, where technician will visit your home for service.


Recently I’ve taken a gas connection of Indian Oil - Indane, India’s largest gas company with nationwide network. It took me Rs. 5400 to get the connection, including IS-4246 high-efficiency gas oven, gas lighter, fire-retardant apron, ‘Suraksha’ LPG hose, regulator, including 1st gas cylinder price and security deposit. Everything is ISI marked, as shown in my YouTube video below.


Now another tip for you, while taking gas connection buying LPG oven is not mandatory, and you can and should bargain on MRP of all the items you’re purchasing while taking the gas connection.

Now coming to the comparison, while using induction, my last bill was Rs. 790 for 125 units. Now cooking solely on gas, for last one full month, bill came Rs. 300 for 50 units. So my electricity consumption reduced by Rs. 490 (75 units).

My first cylinder got emptied this week, lasting 46 days exactly. And subsidized rate of cylinder was Rs. 422 during my purchase. So, my monthly gas expense is 422/46 days x 30 days = Rs. 275. So, a saving of 490-275 = Rs. 215 by using gas is achieved!

Few more advantages of using Gas-
  1. Using double burner oven, you can cook two dishes simultaneously.
  2.  It’s faster that induction, 1.5x to 2x times faster for single oven, for double oven it can be 4x to 5x times faster.
  3. It has low maintenance compared to induction.
  4. It’s economical, as you don’t have to invest in special ‘induction cookware’, you can use any utensil on gas.
  5. You can prepare any dish on gas effortlessly, specially Roti/Chapati.
  6. Can work 24x7, even during power supply outages.

ONE ANNOUNCEMENT!
====================
I'm a YouTube Partner from India. I've uploaded videos on Statistics,Numerical Methods,

And a series of videos showing how to use your scientific calculators Casio fx-991ES & fx-82MS to do maths easily.

Click my YouTube channel's link below to watch them.

 http://www.youtube.com/sujoyn70

Please 'SUBSCRIBE' to my YouTube channel to get updates about my latest video uploads!

Sunday, May 15, 2016

Cisco Router Rommon Mode Problem_How to Get a Cisco Router Out of Rommon Mode_Cisco Router Rommon Recovery_Configuration Register Value 0xF_Cisco 1812 Router Restarts Frequently

Hi, I'm Sujoy from India and today I'll tell you how to recover a Cisco router from Rommon> mode. Also tell you how to recover a Cisco switch from Switch: mode.
Do you know Cisco 1812 router can restart frequently if the config-register value is misconfigured to 0x2102 instead of 0xF.

What is Rommon?
Rommon> or ROM MONitor is the bootstrap loader program stored in ROM (Read Only Memory) of Cisco Router. Which does basic things such loading IOS and booting the router. Another thing is Configuration Register, this is a software register which tells Cisco router what to do during boot. By changing configuration register value, we can do useful things such as password recovery of Cisco router. Cisco router can enter rommon mode for few reasons-
  1. Configuration register value modified
  2. Break (system interrupt) is given during boot (by Ctrl+Pause/Break)
  3. IOS file is corrupted or missing or unsupported
I recently faced a problem where customer lodged complaint that Cisco router is not reachable from remote via telnet or SSH, router can not be pinged also. But the router is powered on. When connected console with router, I found that the router is in rommon 1> mode.

You can type ? (question mark) and press enter to see available commands in rommon mode.
I wanted to if there is an IOS file present in flash memory (cisco router stores IOS file in Flash Memory).
I given command- dir flash: and saw that IOS file present is- c181x-advipservicesk9-mz.124-24.T5.bin

I instructed router to boot from that IOS file using command- boot flash:c181x-advipservicesk9-mz.124-24.T5.bin

Router booted and entered into Router> prompt (or hostname> prompt here). It may ask for username & password if configured.

Type enable and press enter to go to Router# prompt. It may ask for enable password if configured.
Now type config t and press enter to go to Router(config)# prompt. Then give command- do dir to see available files in flash memory. Then select and copy the IOS file name. Now give command- boot system flash:c181x-advipservicesk9-mz.124-24.T5.bin

Next to check configuration register value, give command- show version
Last line shows configuration register value. Default configuration register value on Cisco router is 0x2102 and on Cisco switch it's 0xF .But this is old router (Cisco 1812) which has 10 fast ethernet ports, much like a switch, so default configuration register value is 0xF
Solution- This router had the configuration register value set to 0x0 that's why it was going to rommon mode every time it's reloaded. Change it to 0xF


Router#config t
Router(config)#
Router(config)#do dir
Router(config)#boot system flash:c181x-advipservicesk9-mz.124-24.T5.bin
Router(config)#config-register 0xF
Router(config)#do wr
Then reload the router. Router should boot into Router mode this time.
On other Cisco routers, change configuration register value to 0x2102 for normal operation.
On Cisco Switches, change configuration register value to 0xF for normal operation.

Configuration Register Values and Their Meaning-
0x2102 = Load IOS from flash and load startup-config from NVRAM. (default value)
0x2142 = Load IOS from flash but don't load startup-config from NVRAM. (Router will go into setup mode, asking you to enter initial configuration. Used for password recovery.)
0x2100 = Directly go to Rommon mode
0x2101 = Load Mini IOS from bootflash/ROM (not available on all models)

But what if the IOS file is missing/corrupted on flash memory? Then you've to use TFTPDNLD to recover it. Below are links to my video tutorials on YouTube.

Cisco Router Romon Recovery by tftpdnld- https://youtu.be/7ZjIWMdtmMc
Cisco Router Password Recovery- http://youtu.be/_jPnlAV6NR8
Cisco Router Initial Configuration and WAN Setup- http://youtu.be/saqDIaUDC9g
Cisco Catalyst Switch Password Recovery- https://youtu.be/i1bbWiPosRM
Cisco L3 Switch IOS Upgrade- https://youtu.be/F7dLK1IB-ko
Tellabs Leased Line Modem & Cisco Serial Interface Troubleshooting- https://youtu.be/TuPWULL4V8o

ONE ANNOUNCEMENT!
====================
I'm a YouTube Partner from India. I've uploaded videos on Statistics,Numerical Methods,

And a series of videos showing how to use your scientific calculators Casio fx-991ES & fx-82MS to do maths easily.

Click my YouTube channel's link below to watch them.
Subscribe to my youtube channel below-

 http://www.youtube.com/sujoyn70

Please 'SUBSCRIBE' to my YouTube channel to get updates about my latest video uploads!

Thursday, May 5, 2016

ISDN PRI Troubleshooting and RJ-48 Ethernet Loopback Test on Cisco Router_Primary Rate Interface Problem Fixed_NetworkingTelecom Field Engineer Guide

Hi, I'm Sujoy and today I'll show you how to troubleshoot ISDN Primary Rate Interface (PRI) line and determine working status of ISDN PRI Multiflex Voice WAN Interface Card on Cisco router.

I recently faced a problem where customer can't communicate over the ISDN PRI leased line. I had to do a loopback test on PRI interface to determine if the problem is with ISDN PRI line or PRI card on Cisco 2921 Router. I'll show you how to do step by step troubleshooting.

Step 1- Look at the picture below. It shows VWIC2-1MFT-T1/E1 card on Cisco 2921 router.
VWIC2-1MFT-T1/E1 stands for Voice WAN Interface Card v2 - 1 Port Multiflex Trunk T1 or E1 line card.


Check physical layer status, first look at the card and the interface. If the Ethernet cable is connected and LEDs are glowing then the interface is up. If cable is not connected, connect the cable coming from PRI adaptor and check if interface is up. If not up, check if interface is administratively down and check other configuration.

Step 2- Below is the picture of PRI-to-Ethernet adaptor which converts ISDN line to standard RJ-48 Ethernet line for terminating to Cisco router.


Check the PRI to Ethernet adaptor if any wire got disconnected. If not, we'll move on to Router troubleshooting.

Step 3- Establish a console or telnet session with router and go to Router# prompt (privilege mode). Give command- show inventory and check if the PRI card is showing in inventory. In our case, it's detecting and is highlighted in picture below. If it's showing, then the card is assumed to be ok.

Step 4- Now from Router# prompt give command- show isdn status and check layer 1 status. In our case, layer 1 is SHUTDOWN. If layer 1 (physical layer) is SHUTDOWN, then layer 2 (data link layer) and layer 3 (network layer) will not be able to function.

Layer 1 can be SHUTDOWN due to few reasons- 1) Card is faulty 2) Signaling or keepalives not being received from ISP side 3) wrong configuration 4) Ethernet cable not connected 5) Interface is administratively down. I know reasons 4 and 5 are not valid. I've to identify reasons 1, 2 and 3.

Step 5- Check running-configuration. From Router# prompt give command- show run and gather few information shown in below picture.
card type
controller type
serial interface number
voice-port number

Check if any recent configuration changes have been done. If there are no recent configuration changes done on router before PRI line went down, then it can be issues with PRI card or line. You can check that by command- show run

Router# show run
Building configuration…
Current configuration : 9363 bytes
!
Last configuration change at 13:54:46 IST Wed Apr 20 2016 by Admin

If no configuration changes are done, then we'll move on to loopback test.

Step 6- Check controller status. From Router# prompt give command- show controller e1 0/0/0 and check status up/down. Notice in line number 7, Framing is NO-CRC4 and Line Code is HDB3. These values are generally ISP provided and cause line down if mismatch. Try changing them and see if this works.
Also check if controller, serial interface, voice port is administratively down. If so, enable them by no shutdown command.

Step 7- If that did not work, we need to do loopback test to identify if the problem is with router & card or ISP/telco PRI line.

For this test, I need a Ethernet Loopback Plug. How to make Ethernet Loopback Plug ? Take any ethernet cable and cut after three inch. Now hold the RJ-45 plug keeping pins below and locate pin 1,4, 2, 5. Peel plastic cover of above pins and short copper wires together. Short pin 1 and 4 together and pin 2 and 5 together. Bend slightly outward to avoid short circuit between this two couplings.


Step 8- Connect the loopback plug to PRI interface. And check if LED is glowing. If not, wiring is wrong.



Step 9- Now for loopback test we'll look at the running-config. We derived it in step 6.
In our case, card type e1 0 0 (means e1 card, slot 0 and subslot 0), controller e1 0/0/0 (same as card type,device/slot/subslot), interface Serial0/0/0:15 (it's virtual serial interface for communication), voice-port 0/0/0:15 (voice ports). Give below commands-

Router#config t
Router(config)#controller e1 0/0/0
Router(config-controller)#no pri-group timeslots 1-31
If the above command is accepted, then ok. Otherwise you've to do few more steps.
Router(config-controller)#no pri-group timeslots 1-31
%controller must be shutdown before unconfiguring pri-group to gracefully bring down isdn.
Router(config-controller)#shutdown


Step 10- Shutting down the voice interface. If it gives an error like the one below-
%voice interface must be shutdown before deleting pri-group.
Then give below commands-
Router(config-controller)#exit
Router(config-controller)#voice-port 0/0/0:15
Router(config-controller)#shutdown


Step 11- Removing layer 3 binding.  If it gives an error like the one below-
%Remove layer 3 binding first
Then give below commands-
Router(config-controller)#exit
Router(config-controller)#int Serial0/0/0:15
Router(config-controller)#no isdn bind-l3 ccm-manager

Router(config)#controller e1 0/0/0
Router(config-controller)#no pri-group timeslots 1-31
This time the pri-group command will be accepted. Sometime you may have to give below command to create the serial 0 interface.
Router(config-controller)#channel-group 0 timeslots 1-31

Step 12- Assigning IP address for loopback test.
Router(config-controller)#exit
Router(config)#int Serial0/0/0:0
Router(config-if)#encapsulation hdlc
Router(config-if)#ip add 10.10.10.10 255.255.255.0
Router(config-if)#no shutdown


Step 13- Checking Serial Interface status and enabling controller e1.
Router#show int Serial0/0/0:0
Router#config t
Router(config)#controller e1 0/0/0
Router(config-controller)#no shutdown


Step 14- Doing loopback test.
Router#ping ip 10.10.10.10 repeat 1000
If all 1000 pings are getting reply (!) then your PRI card interface is working fine. The problem is with the line. Contact your ISP/telco for line checkup. You can also check that the show controller e1 0/0/0 shows status up.

You can watch video version of this article here- https://youtu.be/rJJGAi-Sdy0

ONE ANNOUNCEMENT!
====================
I'm a YouTube Partner from India. I've uploaded videos on Statistics,Numerical Methods,

And a series of videos showing how to use your scientific calculators Casio fx-991ES & fx-82MS to do maths easily.

Click my YouTube channel's link below to watch them.
Subscribe to my youtube channel below-

 http://www.youtube.com/sujoyn70

Please 'SUBSCRIBE' to my YouTube channel to get updates about my latest video uploads!

Tuesday, May 3, 2016

How to Subnet? Subnetting in a Nutshell for Dummies! Learn Subnetting in 10 Minutes!! [Everything Explained]

Hi, I'm Sujoy from India and today I'll tell you how to solve any subnetting practice questions easily! You may be preparing for your CCNA exam or want to learn everyday subnetting. I'll tell you how to subnet in your head easily.

IP Address Basics- An IP address is a 32 bit binary number, represented in 4 blocks of 8bits each. Each 8bit block is called an Octet. For human comprehension, each octet is written in Decimal form, separated by dots. This representation is called 'Dotted-Decimal Representation'. IP addresses are of 5 'classes', which is generally identified by 1st octet of an IP address.
Class A (0-127), Class B (128-191), Class C (192-223), Class D (224-239), Class E (240-254).
Example- 192.168.1.115, which is Class C address, since first octet 192 falls within range (192-223).

Subnet Mask Basics- Subnet Mask is a 32 bit binary number. Just like IP address, the subnet mask is also represented in 4 blocks of 8bits each. Subnet mask, when written with an IP address, represents which subnet the given IP address belongs. Example- 255.255.255.224 or /27. Here /27 means out of 32 bit subnet mask, first 27 bits are reserved from left.
Subnet Mask Categorization- /8-/15 only for Class A, /16-/23 Class A & B, /24-/30 Class A, B & C.

Let's take a question- 192.168.1.115/27. I'll tell you how to do Eleven subnetting calculations easily.

Weighted Binary Chart (represents an octet)
 27    26   25   24    23  22  21  20
128   64    32    16     8     4     2     1

Let's Begin the Calculation!

1. Subnet Mask- The given ip address is 192.168.1.115, which is Class C IP address, means first 3 octets or 24bits of subnet mask is already reserved (which is 255.255.255.0). Now there is /27, means 27-24 = 3 more bits are reserved from 4th octet. Total 27 bits are reserved.
Now from Weighted Binary Chart, if we reserve 3bits from left, the mask value will be 128+64+32 = 224. So complete subnet mask for this subnet = 255.255.255.224.

2. Block Size- Block size is 2^unreserved bits. Here in 4th octet, 3 bits are reserved. Unreserved bits 8-3 = 5. From Weighted Binary Chart, 2^5 = 32, so block size is 32. Block size is very important.

3. Network ID/Network Address- Now we will count in block of 32, which is our block size.
0-32-64-96-128-160-192-224-256. 4th octet of our IP address is 115, which falls in range 96-128. So our network ID is 192.168.1.96 (by starting value of range).

4. Broadcast Address- It's the last IP address of the subnet. Our range is 96-128. Last IP address is 127, because from 128 next subnet starts (128-160). Broadcast address = 192.168.1.127.

5. Start IP Address- It's the first IP address after Network ID. In our subnet, Network ID is 96, so Start IP address = 192.168.1.97.

6. End IP Address- It's the last IP address before Broadcast Address. In our subnet, Broadcast Address is 127, so End IP address = 192.168.1.126.

7. Range of Valid Assignable IP Addresses for This Subnet- 192.168.1.97 - 192.168.1.126.
These IP addresses can be assigned to host devices (such as PCs in that subnet).

8. Number of Subnets- It's given by 2^reserved bits. Reserved bits are 3, so number of subnets = 2^3 = 8. Let's look at this, 0-32-64-96-128-160-192-224-256. Our first subnet is 0-31, next is 32-63, and so on, total 8 subnets.

9. Number of Hosts Per Subnet- It's given by (2^unreserved bits - 2). Or Block Size - 2. Unreserved bits are 5, and 2^5 is 32 (which is our block size). And 32-2 = 30 hosts per subnet. Let's verify!
Our valid IP address range is 192.168.1.97 - 192.168.1.126. If you count to 126, starting from 97, you'll count 30 addresses.

10. IP 192.168.1.115 is in Which Subnet? It's is fourth subnet. Our first subnet is 0-31, second is 32-63, third is 64-95, fourth is 96-127. IP 192.168.1.115 falls in 4th subnet.

11. Represent 192.168.1.115 in Binary- As I mentioned earlier, an IP address is actually a binary number. Let's write each octet in binary format. We'll use Weighted Binary Chart for this calculation.

128   64    32    16     8     4     2     1
  1      1      0      0      0     0     0     0  =  192
  1      0      1      0      1     0     0     0  =  168
  0      0      0      0      0     0     0     1  =    1
  0      1      1      1      0     0     1     1  =  115

So the binary representation is- 192.168.1.115 = 11000000.10101000.00000001.01110011
Here's the logic- to make 192 (1st octet), we need 128+64=192. We've taken those two bits, and placed '1' below 128 and 64 in Weighted Binary Chart. We didn't take any other bits so we placed 0 below them.
Similarly for 168, we've taken 128+32+8 = 168. So we've placed '1' below 128, 32 and 8, and so on.

You can watch video version of this article here- https://youtu.be/91ZZ7xVLjmU


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