Computer cannot ping a certain IP?

[zelgadis85]

Hello again, good people of TechSpot. I have had several troubles of my own in the past and every time I have found an answer (of sorts) in here, and I thought I'd bug you once again...

I have a friend at work who has a computer that is working fine by all standards, except that it cannot ping a certain IP address. Almost any address pings (we have not found but one that NEVER allows pinging from that computer). I wonder how could this be?

My own computer pings the troubling address just fine.


Any help would be greatly appreciated.

Thanks in advance.

 

[Garfield]

has his machine got a firewall that maybe has flaged the IP address firewall ofter bolck ip address's when the recive odd data tranfer rates from them eg C.O.M.O.D.O forgive the caps its how its spelt can block individual ip addresses get back to me with deatils of os and the security applications one more thing does the machine have static IP address or automatic

 

[zelgadis85]

has his machine got a firewall that maybe has flaged the IP address firewall ofter bolck ip address's when the recive odd data tranfer rates from them eg C.O.M.O.D.O forgive the caps its how its spelt can block individual ip addresses get back to me with deatils of os and the security applications one more thing does the machine have static IP address or automatic

My friend's computer gets it's IP address from DHCP server (he's running Windows XP, SP2 if I remember correctly) while the other computer is a server (of sorts), with it's static IP. I have no idea what is running over there (the computer is in a different building, I haven't been there)

Funny that every other computer can ping the "server", just not my friend's.


But we'll get to the root of the problem, I'm sure of it

 

[DelJo63]

let's understand the layout. You appear to be talking about a network like

yourSystem--yourRouter --yourISPgateway ...... hisISPgateay--hisRouter--hisSystem

You should expect to ping from yourSystem -->any ISP, or even any broadband user's router (eg hisRouter above)
You should not expect to be able to ping hisSystem.

Why?
First, all (ok 99%) systems behind a router have NAT enabled and have
addresses in the private, non-routable address range. Have you ever noticed
that a great many of us have a router address of 192.162.0.1 or 192.168.1.1 ?
That means my system could have an identical address as hisSystem!

Second, most routers are configured to NOT pass ping traffic into the LAN side connections.

Third, firewalls can be configured to not respond to ping.

Do this; get the public IP address of yourRouter and hisRouter. Now ping the
public addresses. If this works, that's the best you can expect.

 

[zelgadis85]

let's understand the layout. You appear to be talking about a network like

yourSystem--yourRouter --yourISPgateway ...... hisISPgateay--hisRouter--hisSystem

Umm... I forgot to tell that I can ping my friend, so this is not exactly the case...

The network is more like

mySystem-myRouter-myISPgateway
hisISPgateway--hisRouter--hisSystem
serverISP--serverRouter--server

I can ping both the server and his system just fine (of course I use public IP addresses ) but he can only ping my system (once again, public IP) but not the server. Other computers can ping the server just fine. (Public IP, but I think I have repeated this enough already :stickout: )

You should expect to ping from yourSystem -->any ISP, or even any broadband user's router (eg hisRouter above)
You should not expect to be able to ping hisSystem.

If you are talking about public vs. private IP addresses, well let's just say I already know the difference.

Why?
First, all (ok 99%) systems behind a router have NAT enabled and have
addresses in the private, non-routable address range. Have you ever noticed
that a great many of us have a router address of 192.162.0.1 or 192.168.1.1 ?
That means my system could have an identical address as hisSystem!

Thanks for the info, but sadly, I knew it already. (In my case I have a different beginning for my private IP, but that's beside the point)

Second, most routers are configured to NOT pass ping traffic into the LAN side connections.

Third, firewalls can be configured to not respond to ping.

I think this can be somewhat ruled out due to the fact the server responds to my ping requests (as well as any other computer we've tried), but not his.


Anyway, thanks for the suggestions. I'll go these things through with him once I see him next time. Maybe we can get somewhere from these tips. I'll keep you updated.


UPDATE: As of now, tracert does not hop EVEN once when tracing "server". It really bugs us out as we can't figure the life out of us as what could cause this..

 

[CCT]

I read that if you have installed Microsoft's IAS server, to act as a proxy server and firewall in addition to its other tasks, the firewall MUST be configured to allow connectivity to the client PCs; by default it blocks virtually all traffic. This would prevent a ping request.


ref: http://72.14.205.104/search?q=cache...annot+ping+a+server&hl=en&ct=clnk&cd=41&gl=ca

 

[DelJo63]

UPDATE: As of now, tracert does not hop EVEN once when tracing "server". It really bugs us out as we can't figure the life out of us as what could cause this..

Tracert uses the ping protocol; if you can't ping it, then tracert will not reach it either

 

[zelgadis85]

Case solved, thanks for all the help

I read that if you have installed Microsoft's IAS server, to act as a proxy server and firewall in addition to its other tasks, the firewall MUST be configured to allow connectivity to the client PCs; by default it blocks virtually all traffic. This would prevent a ping request.

Yeah, it would seem so. Another friend of mine (an IT expert) found out that this was indeed the case. In our case, though, the conflicting software was found out to be VMWare. There seemed to be certain settings we had overlooked, but once he changed some of them, PING started to work normally (just like TRACERT).

I appreciate all the help you have given and am content to call this case solved and closed.