why is 'Ping' used?

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??

Mayank

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

Yeah! U cleared out the doubt very well Mayank....Thanx

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

crook

Quote:

Originally Posted by 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

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

nice and quite technical repleis mayank...
didnt know abt this b4... kool

Mayank

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

crazyboy · 07:38 PM

Quote:

Originally Posted by 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

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.