Can't ping localhost, but can ping everywhere else!

Hi all:

I've been lurking here for a long while, but just registered today, because I need some help.

First off, sorry for the long post. If you want the short version, just scroll down to the bottom!

I have a Sony laptop, VGN-FS760/W that's 3 years old, and has been working fine. Of course, everything works fine just before it breaks...

Anyaway, I've been having trouble with it hanging, taking forever to shut down and/or start up, and hanging on anything to do with networking/Internet.

It seems to work fine sometimes, then is horrendus at other times. For instance, it worked great all day yesterday, for 8 hours straight. But then when it was time to shut down, it took about 20 minutes!

So, I've been doing all sorts of things to narrow this down. For instance, I've gotten a new drive, installed the original CDs, and started from scratch.

Then it worked fine. Sort-of. After a day or two, it started doing the same thing.

Then I got the idea that the "hanging" was actually various software trying to do an Internet connection. Just to see which ones were, I installed ZoneAlarm, and told it to alert me to every connection.

I was amazed at all of the software that talks to the Internet! MS Word, Adobe Photoshop, etc., etc., all connect, presumably to check for updates, and so forth.

So, in order to further track this down, I started doing some network checks whenever it hung. I pinged my DNS server, various websites, and had no problem. Then I pnged localhost and... it timed out! When it's hung up, I can ping anywhere in the world, but can't ping my own computer!

Today I decided to eliminate everything at my house, and plug the laptop directly into the router when/if it hung.

I worked for a few hours today, and when it hung, I unplugged the power cord, so I could run to the router with the laptop. Guess what? The problem went away!

===> Short Version!

So, from time to time my computer hangs, whether connected by wireless or wired, and I can ping anywhere in the world, but I cannot ping localhost.

For the rest of today, whenever my computer hung, I unplugged the power cord, and it "cured" itself!

So, now that I've determined that the power supply has something to do with the problem, the question is... Why?

Why, and how, could the power supply affect pinging only localhost?

The only thing I can think of is that the Sony power monitoring software has something to do with it. They have a silly little icon in the tray that is supposed to show the battery status, time remaining, and whether AC is on.

Any ideas?

 

What happens if you try pinging the IP your router assigned to your computer in circumstances where you cannot ping localhost?

 

Hi Shyster:

When it hangs, all of the following pings will time out:

localhost
127.0.0.1
192.168.0.x (the actual IP address currently assigned to the laptop.)

So far, every time that I pull the power cord out of the laptop, it resumes.

 

Further development...

I have a USB cooling pad plugged in, and it seems that it may be part of the problem.

The computer is hanging a lot today (good for diagnostics, bad for productivity!) and I've noticed that unplugging the cooling pad will also restart the pings.

So, I've just plugged the cooling pad into its own, separate power supply.

We'll see how this goes.

Stay tuned...

Update:

It seems that there's no difference, whether the cooling pad is plugged in to a separate PS, or if the cooling pad is off altogether.

It's very intermittent, so tough to really be certain what is affecting the problem...

 

When it's not pinging, check your hosts file, see if there's anything funky in that. Some viruses and such will modify that file.

http://en.wikipedia.org/wiki/Hosts_file#Location_and_default_content

 

I'm guessing here, but it sounds like there might be an issue with the power management for your NIC. Have you changed any of the power settings on the wireless NIC lately? If not, check them to see what they're set at, and also try changing them to see if that affects any of the observed behaviours.

 

Check your firewall setting, I know some firewalls that block ping requests. (I used to use zonealarm and I vaguely remember that it blocks ICMP packets sent by ping request), try turning it off for a moment and see if that allows you to ping localhost.
Some routers also support this function as well, but usually on the WAN side, and not for internal addresses.

 

Hi PitaBred:

I just checked the hosts file. Here's what is has:

127.0.0.1 localhost

Good idea, and one I hadn't thought of. But it looks like that's not it...

Thanks!

 

Hi Pai:

Good idea on the firewall!

At one point I had tried to shut off ZoneAlarm, and see if that made a difference. It did not.

I reasoned that ZoneAlarm would not be the problem, since the ping problem is not consistent.

For example, as I write this, pings to localhost are working fine, with the power plugged in. But the pings do stop, and removing the power cord will restart them.

I can't imagine that ZoneAlarm would change settings on its own, only to have the settings restore when the power cord is unplugged...

So, lacking any further reason, it's probably best to assume that ZoneAlarm is not the cause.

 

Hi Shyster:

Power management, eh? Let's see...

I had changed it at one point, but I changed everything to "always on." I was thinking that maybe power management had gone mad, and was shutting something down on its own.

Now, let me see if there's a power management setting for the internal wireless...

Yes, there is. The NIC is an Intel Wireless Pro 2200BG, BTW. And I had changed the setting on that, during my diagnostic quest. Here are the choices:

Select a balance between power consumption and adapter performance.
Default: Power settings based on computer's power source.
Lowest: Maximum battery life.
Highest: Maximum performance.

I had set it to "Highest - Maximum Performance."

I'll change it back to "Use Default Value" and see if that helps.

Thanks!

 

Hi Shyster:

I changed the power management on the NIC, but it didn't seem to make any difference.

I decided that the "unplug the power cord" thing was the only consistent thing that I've found with this problem.

So, I ran out to the local Sony Style Store and picked up a new power supply.

Ouch! $95.00!!!

Anyway, I've had it plugged in for over three hours so far, and no problem.

So, the big question is... how and why is the power supply stopping my computer from pinging localhost?

I have never run into anything even remotely like this.

I can't imagine why localhost would not ping, but everything else does...

 

your firewall is more than likely blocking ICMP traffic (pings)

 

Hi D-:

[your firewall is more than likely blocking ICMP traffic (pings)]

One would think! But a firewall problem doesn't seem to make sense, here.

What is the explanation for the firewall blocking intermittently? And for allowing pings when the power cord is unplugged?

And then blocking them again (intermittently) when the power cord is back in?

If it were the firewall, wouldn't it always block? Or always not? (assuming someone or something isn't changing any firewall settings)

And why doesn't the firewall log show these attempts and/or blocks?

And, best of all... why hasn't the firewall blocked a single ping (I've got it pinging continuously) for the last 7 hours, since I started using the new power supply?

Very strange...



Oh, and here's another one for you... I just double-checked, and the "trusted zone" (local network) firewall security has been turned off!

I would expect that the firewall would consider localhost to be in the trusted zone, and therfore not block it when trusted zone security is turned off...

 

You do have a very peculiar problem, but it's also reproducible almost on command, so it should be possible to eventually track it down (if you're so inclined). Just off the top of my head, there are a host of different things that the power supply is related to that might cause problems with the NIC or even with one of the various protocol drivers. The most obvious is the comprehensive power management systems that vary the configurations of a whole host of different components based on changing power levels.

One way to start trying to find the thread that connects the power supply to the network ping is to download and run Sysinternals' Process Explorer. That tool can be overwhelming at first because it's so powerful; however, if you watch what happens with the old PSU in and out, with the problem occuring and not occuring, you should be able to spot which process is involved, and from there drill down to find the particular difference that's causing the problem.

Another tool you might play with is Microsoft's Network Monitor 3.2. This tool will monitor the traffic on your network (not all, but most, and everything that comes from, or goes to, the system on which it's running). Try firing that up and then pinging yourself with, and without, the problem occuring to see what sort of packets are being sent back and forth, and see if there's any discernible difference based on the occurence or non-occurence of the problem.