How ping works with machines in different subnet ?

As stated earlier a packet will be created like below

Destination IP

Source IP

Data

Protocol field

 

Now when you ping from the source to destination,

àThe ARP table is checked for the MAC address of the destination , then it sends out an ARP broadcast, even then it is not found

àNow the ARP and IP protocols conclude that the destination is in a different system and start off with the next phase of work.

 àIn Windows machine, the registry is consulted and the default gateway IP address is found.

àNow  a request is sent out with the default gateway IP in the destination field querying for its MAC address. If there is no response then an ARP broadcast is sent. After which the default gateway’s MAC address is learnt.

à The router’s interface which would be the default gateway for the system also stores the MAC address of the source A in its cache. Now the router is aware of the system A’s MAC address and the system A is aware of the Router’s interface (default gateway) MAC address.

 àNow the system A knows where to send the packet next and sends the information to the data link layer and the frame is in the following format.

Destination MAC(default gateway MAC)

Source MAC(system A's MAC address)

FCS(Frame check sequence)-to make sure that the integrity of the packet is not lost

Ether type field(used to find which protocol is encapsulated in the frame, here it is IP)

 

àNow the system passes down to the physical layer and gains entry into the router. This is placed on the wire bit by bit.

àNow the packet gains entry into the router via the default gateway.

àAgain the Data link layer is checked and torn open to take out the IP protocol details.

àThe destination IP would be the system B’s IP and.

àSince the packet has gained entry into the router, the router will have the information of all the hosts in the subnet it lies.

 àNow the ARP cache of the router is checked if the MAC address of the destination IP is available. It would be found or an ARP broadcast is sent and it reaches all the hosts in the subnet.

àThe MAC address that belongs to the IP responds and thus the connectivity from system A to system B is established.

 
àBut this is not the end , the same process is repeated for the return packet as well.

àI think you should now recollect the three types of responses you receive when you ping a machine.  If the connectivity from system A to system B is alone established, think what would be the message you receive,

“Request timed out” is the right answer as you think.

What happens while pinging destination on the same subnet

Hello Everyone,

Once I have tried to find this information online before where I couldn’t find what I exactly wanted.

So I have decided to give this information to you in very simple terms with more technical information.

When you type ping  <ip address>,  the IP protocol creates a packet like below

Destination IP

Source IP

Data

Protocol field

 

You must be wondering why is this protocol field here, that’s not a bad question to ask.

The protocol field has the protocol which should be used by the destination to process the packet according to the request. In this case it is ICMP. Ping works on ICMP.

Also the value of the protocol field would be set to 0x followed by a hexadecimal number and this indicates that it is ICMP.

Now the ARP (Address resolution Protocol) starts its job. There will be an ARP table maintained in every system. ARP is nothing but a protocol which helps to look up the MAC address of a given IP.

 

Since both the source and destination are in the same subnet i.e. there is no layer 3 device that comes in between to do the routing, the ARP checks its cache to lookup the MAC address of the IP mentioned in the destination field. If it is not in the cache, then an ARP broadcast is sent out (ff:ff:ff:ff:ff:ff)

 

It would be either found in the ARP table or by the broadcast, the recipient replies the MAC address and the ARP table gets populated and the packet gets delivered to the destination.

A basic question here, how does the system differentiate if the destination lies in the same subnet or a different one.

If subnet mask is your answer, then you are absolutely right.

Basic analysis and troubleshooting internet with PING operation

Nowadays we can’t imagine the impact when your Internet browser says “Internet Explorer cannot display the webpage”

So it is always good to know the basic troubleshooting to identify the problem and resolve it.

When you are ready for troubleshooting then you should know the command “PING”

What is Ping ?

Ping has become very usual and there cannot be many people who do not know the meaning of this wonder word.

PING- stands for Packet Internet Gopher

You want to check if there is connectivity to some destination. Ping makes your job very simple.

All you have to do is

Open up command prompt in case of windows or the “terminal” incase of Mac and type

Ping  89.69.69.6( the IP you want to )

Tada..you get three types of responses

1.       Reply from 89.69.69.6 (Meaning there is reach ability from your machine to the destination)

2.       Destination host unreachable (There are no routes configured for the destination and there is absolutely no connectivity).

3.       Request timed out ( Meaning you are able to reach the destination, but there is an issue with the reverse path i.e. from the destination to your machine and hence the connectivity is not completely established)

So finally when you get a reply we can conclude that it is not a network issue.

Problem could be with your browser, antivirus, virus infection.

Solution could be the below:

1.       Reset your browser

2.       Run scan with your antivirus.

3.       My personal experience is download Malwarebytes and run it.(if it Is affected with  virus)

Now we understood the importance of ping operation.

To make it more interesting and useful for lovers of technology I will explain about ping from same subnet and different in my next blog.

To read more on ping you can refer to Wiki

Country with fastest and cheapest internet

Do you know which country enjoys the Fastes and cheapest internet?

Any Guess?

US, UK, canada or some European country. Absoultely not.

Hong Kong has the best internet speed 49.2 Mbps. They achieve this with the "Fiber To The Home"  technology.

So what about the bigger and stronger countries like US and India.

United states hold 11 the rank with 27.1 Mbps and Inia holds 116th psoition with 6.9 Mbps.

Lets hope to get more speed in future !!

Check this for more info

http://www.siliconindia.com/news/technology/10-Countries-With-Best-Internet-Speed-In-The-World-nid-133791-cid-2.html