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Neha
Neha • Jul 12, 2006

Why is 'Ping' used?

I have often seen people doing Ping with IP(internet Protocol) address in continuation when the server is down...Can anyone write down what does it mean and why is it used??
Mayank
Mayank • Jul 12, 2006
Answer: Why "PING"

Hi,

"PING" is fundamentally an ICMP echo request program. The main idea is to check the reachability and availability of a desired host. ICMP stands for : Internet Control Message Protocol. Actually this a part of the IP layer in the TCP/IP protocol suit.

Mechanism:
A m/c on N/W issues an ping request(ICMP echo request) to another m/c on the network. That m/c when receives this request formulate an ICMP echo response and sends back to the m/c that generated the request. The datagram also have some space for optional data and other stuffs.

So, if the target m/c recieves the echo request, then that means the intermediate links, routers and of course the target m/c is correctly funtioning till their IP layer. The same is verified for the return route opted by the response datagram(response route may be diff than the request route).

Note:
ICMP - This protocol is responsible for the control messages that flow across the N/W for traffic control, congestion control and many more stuff. There are 'n' no. of variation available for "ping" itself, but no need to go to so much details.

Hope this reply will clear all ur doubts regarding "PING" at least.

Regards,
Mayank
Neha
Neha • Jul 13, 2006
Yeah! U cleared out the doubt very well Mayank....Thanx
crazypal
crazypal • Jul 13, 2006
Nice explanation Mayank...
Can you answer few of my queries...

Is it possible that one won't able to PING a machine and able to telnet it...??
thanks in advance...
--Crazypal😁
crook
crook • Jul 13, 2006
yes i think

crazypal
Nice explanation Mayank...
Can you answer few of my queries...

Is it possible that one won't able to PING a machine and able to telnet it...??
thanks in advance...
--Crazypal😁
I think you can telnet a machine even when the ping is not working. Not sure though. I had tried that when I during our computer workshops. 😕

Crook
Mayank
Mayank • Jul 13, 2006
Solution is a tweak :d

Hi,

Ideally speaking this cannot/shudnot b done. The way is to disable ur System to reply to ICMP echo requests. One shud not go for such a configuration coz that may result to other issues may be loss of data. Anyways this is how it is implemented.

On Win XP:
Login to the machine as an admin.
Start -> Control Panel -> Network and Internet Connections -> Network Connections.
Right click on the netwaork connection u see there.
Properties -> Advanced -> Settings -> Advanced
In the ICMP section select Settings....
Here on the top u'll get an option to disable echo requests from remote systems. Uncheck that.
Apply those settings. U are done.

On UNIX systems the following command shud work:
/sbin/ipchains -A input -j DENY -i eth0 -p icmp -s
0.0.0.0/0 -d 0.0.0.0/0
Just note one thing that this will not just restrict others to ping u
but also restricts u to ping others.

Note: This functionality cud also b implemented if u configure ur
router or the firewall to filter and dump the ICMP echo req/reply
packets.

Hope this satisfy your apetite of querries. You know such apeptite
is really very good for one to have.

Great Question.

Thanks and Regards,
Mayank Shukla
aashima
aashima • Jul 13, 2006
thats great!!!

nice and quite technical repleis mayank...
didnt know abt this b4... kool
Mayank
Mayank • Jul 13, 2006
Thanks...

Hi,

Thanks for the appreciation. On top of that i wud like that we all CE'ians shoot this(our) forum with all the technical stuff and nething n everything of similar nature. So, in turn we will be helping the whole INTERNET community with our stuff and in due course will definitely groom ourselves.

Common buddies lets rock the world together.

Mayank Shukla
Mayank
Hi,

Ideally speaking this cannot/shudnot b done. The way is to disable ur System to reply to ICMP echo requests. One shud not go for such a configuration coz that may result to other issues may be loss of data. Anyways this is how it is implemented.

On Win XP:
Login to the machine as an admin.
Start -> Control Panel -> Network and Internet Connections -> Network Connections.
Right click on the netwaork connection u see there.
Properties -> Advanced -> Settings -> Advanced
In the ICMP section select Settings....
Here on the top u'll get an option to disable echo requests from remote systems. Uncheck that.
Apply those settings. U are done.

On UNIX systems the following command shud work:
/sbin/ipchains -A input -j DENY -i eth0 -p icmp -s
0.0.0.0/0 -d 0.0.0.0/0
Just note one thing that this will not just restrict others to ping u
but also restricts u to ping others.

Note: This functionality cud also b implemented if u configure ur
router or the firewall to filter and dump the ICMP echo req/reply
packets.

Hope this satisfy your apetite of querries. You know such apeptite
is really very good for one to have.

Great Question.

Thanks and Regards,
Mayank Shukla
Good job Mayank...
Sorry, I must say good try ......

What i guess Is..... It is quite possible that we will Ping a machine and we will get Request time out and at the same time we can Telnet that machine.
So your basis of saying that ... if a machine is up and in network ... you will able to PING it is wrong... Do me correct if i miss interpret you... And about the setting you mention for Windows are not available in older version of the windows??
Is it... I experienced on one win 98' that it was not there ...

I am not sure how we can do this but one way of doing this is keep your machine on External IP or .... there must be somesetting which will keep the machine out of reach from other user when they try to PING the machine.

What you think Mayank...??

--Crazy
Mayank
Mayank • Jul 17, 2006
Hey Crazy,

Sorry BOSS I am not able to get u 100 %. But still to make it better I'll try to put the stuff in a clearer way.

1. The setting that i mentioned in my previous post is only for WinXP, as u didnt found it on Win98 thats pretty obvious. Anyways, Win98 is not an N/W Operating System, whereas WinXP, Win2003 Servers n all are, so u can never get these advanced settings in Win98 at least.

2. When u apply these setting:
a. U'll get request timeout on doing a "PING" to that m/c but u can telnet on it successfully.
b. Now see wat happens behind the scenes:
* ICMP Echo Response from ur m/c are disabled(IP Layer).[ Just a part of one[ICMP] of the many[IGMP,ICMP,IP,ARP,RARP....] protocols implemented at IP layer is disabled]
* Telnet, an Application Layer Protocol is still working which internally do not uses PING, so it works perfectly fine.

3. As far as u said about keeping ur m/c on an externel IP, I agree to it. As I previously metioned that this cud be done when ur router or the Firewall has specific settings to filter n dump all the PING requests targeted at ur m/c.

Further querries and suggestions are invited.

Thanks and Regards,
Mayank Shukla.
Mayank
As far as u said about keeping ur m/c on an externel IP, I agree to it. As I previously metioned that this cud be done when ur router or the Firewall has specific settings to filter n dump all the PING requests targeted at ur m/c.

Further querries and suggestions are invited.

Thanks and Regards,
Mayank Shukla.
Nice Explannation Mayank...

Can you elucidate something on matter of External Ip...

Thanks in Advance.
--Crazy
pradypop
pradypop • Jul 18, 2006
Telnet uses TCP over IP, and has nothing to do with ICMP. Ping wont work if echo-servers are not installed. That simply doesn't mean Telnet doesn't work. Ping is used for testing the network.

But for a common user, ping as an application and its associated protocols are almost always installed on all systems. So, if ping does not work, Telnet might not work as well because the system you are attempting to connect is not available.

Ouote:
Telnet, an Application Layer Protocol is still working which internally do not uses PING, so it works perfectly fine.

Telnet and ping both are applications. Ping is not a protocol and will not be used by Telnet anyways. Ping uses UDP over ICMP. Telnet uses TCP over IP.
pradypop
pradypop • Jul 18, 2006
Most organizations lease out only one IP address. Does that mean We can connect internet to only one system? That's not the case. The IP which we lease out is external IP, the one which is visble externally on the net.

All our systems are connected on LAN with IPs generally of form 192.168.x.x. We can call these as internal IPs. All PCs on LAN hide behind the external IP to communicate with internet. This is generally done using NAT masquandering. That means these PCs are not visible from internet and cannot be pinged directly.
sgurucharan
sgurucharan • Oct 10, 2006
Neha
I have often seen people doing Ping with IP(internet Protocol) address in continuation when the server is down...Can anyone write down what does it mean and why is it used??

Hi Neha

PING is command to check the connectivity across the network
So , when a server down frist job to check the connectivity
so we use command PING
Syntax is ping (IP Address)
crazy
crazy • Jan 20, 2007
hi dear, Ping is use basically to know the connectivity of the server ...
wherther the server is down or running..And the other purpose is that
if it pinging then its come to know that someone is online on dat local network.
mahul
mahul • Nov 15, 2007
hey mayank u might not believe this bt this is 100% true.this evening i was setting up a lan connection and one machine responded when pinged from a second machine bt the second did not respond when pinged from the first. can any1 explain this?

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