# Destination host unreachable



## psynaptic (Sep 24, 2006)

Hi there,

I'm having a nightmare trying to resolve this issue so I thought I'd put it up here to see if anyone can shed a little light on the situation.

Here it goes..

When I ping or tracert it says '1 Destination host unreachable'. 

My browser, ftp, ssh, email, everything is working fine. The problem is when I am connected to my remote host it drops the connection for between 5-20 minutes at a time. I thought it was the server going down and have been in contact with the provider all day trying to resolve it. They have told me that their server has not experienced any down time and tried their best to suggest options to try and resolve this.

So far I have:

Released and renewed my IP
Shutdown and rebooted my computer and cable modem
Uninstalled zone alarm firewall and disabled the windows xp sp2 firewall
Manually configured my IP, gateway and changed the dns servers
Flushed the DNS, rebooted computer and modem
Checked my hosts file which only has '127.0.0.1 localhost' set

I seem to be behind a transparent cache but do not know if this will make a difference to the ping or tracert and if fixing this will resolve my bigger problem.

Does anyone have an idea which might help me resolve this?

Thanks a lot,

Rich


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## InspectorGadget (May 14, 2005)

If you're able to connect to a service (web browsing) on a given host but cannot ping or traceroute, either the desitnation server is blocking incoming ICMP, or your ISP or computer's firewall is blocking outgoing ICMP and/or traceroute.



> The problem is when I am connected to my remote host it drops the connection for between 5-20 minutes at a time.


Please be more descriptive. "connected to my remote host" is too vague. Describe exactly what you are doing (web browsing, ftp, etc.), then describe what it looks like when it "drops the connection", and describe what happens when the connection resume. Does it ever resume without any action on your part aside from waiting for a while?



> I thought it was the server going down and have been in contact with the provider all day trying to resolve it.


What does this mean? By "server going down" do you mean your internet connection was disabled?

One of your problems may be that you are using technical terms incorrectly. Best to stick to visual descriptive terms -- say what you are doing and what you observe happening instead of technical jargon.

- The Inspector


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## psynaptic (Sep 24, 2006)

Thanks for your reply.



> If you're able to connect to a service (web browsing) on a given host but cannot ping or traceroute, either the desitnation server is blocking incoming ICMP, or your ISP or computer's firewall is blocking outgoing ICMP and/or traceroute.


I cannot ping www.google.com which I know isn't blocking incoming ICMP. I rebooted in safe mode with networking and can ping it fine so it must be a problem with my firewall. I use Zone Alarm with Anti Virus and when I first discovered I was unable to ping I thought it might somehow be causing the problem. I uninstalled it but had to manually remove certain files, folders and registry keys which were left on the system. I have since reinstalled it and configured it to allow pings but it still won't work.



> Please be more descriptive. "connected to my remote host" is too vague. Describe exactly what you are doing (web browsing, ftp, etc.), then describe what it looks like when it "drops the connection", and describe what happens when the connection resume. Does it ever resume without any action on your part aside from waiting for a while?


I have been transferring files to my web hosting server using FTP and Dreamweaver. Sometimes when I am using FTP to transfer folders of files it will timeout somewhere during the transfer queue and it will keep trying to reconnect to finish the job. It will eventually reconnect and complete the job but it is annoying having to wait at times I am trying to be productive. There is no action from me apart from making a cup of tea while I wait for it to sort itself out. I also use shared ssl provided free by my host (only a temporary measure) and this server is the same as the one I use to connect to for FTP. It is also the same as my email server and all of these 'services' fail when this happens. I cannot send emails, FTP files to that server and pages in my browser which are through HTTPS do not load. This is why I thought their server was 'going down'.



> What does this mean? By "server going down" do you mean your internet connection was disabled?


I meant that I thought the web hosting server was unhealthy and being rebooted often. Either that or having some sort of intermittent connectivity problems.

If you have an input it will be much appreciated.

Rich


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## InspectorGadget (May 14, 2005)

Rich,

Thank you for the good information.

It sounds like the Ping problem is separate from the FTP problem. Try disabling Zone Alarm and Anti Virus and pinging again. But I don't really think Ping matters if you can connect to FTP servers and access web pages.

The FTP timeout is the most interesting symptom. If FTP gradually slows down and stops, it is a symptom of lost packets or extremely long latencies passing through your ISP. FTP is very sensitive to the quality of the connection. If FTP is failing with timeouts, it suggests a lousy ISP connection or upstream routing.

Try this for me... type this into a Command window (DOS box):

tracert www.google.com

Also, substitute the name of your FTP server in place of "www.google.com".

Then copy and paste the results into a reply.

- The Inspector


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## psynaptic (Sep 24, 2006)

Hi Inspector,

Thanks for your reply.

I shutdown Zone Alarm and checked that the Windows firewall was switched off. I ran the tracerts and here are the results:

Google:


```
Tracing route to www.l.google.com [66.249.93.147]
over a maximum of 30 hops:
  1  Destination host unreachable.
Trace complete.
```
FTP Server:


```
Unable to resolve target system name server.myhostname.com.
```
It just so happened that I was experiencing the problem when I ran these and as you can see it looks like the FTP server is not available.



> The FTP timeout is the most interesting symptom. If FTP gradually slows down and stops, it is a symptom of lost packets or extremely long latencies passing through your ISP. FTP is very sensitive to the quality of the connection. If FTP is failing with timeouts, it suggests a lousy ISP connection or upstream routing


All the ways in which I connect to the server: FTP, web browsing, SMTP, IMAP, etc. all stop working when this problem occurs. This is why I initially thought the server was 'going down'.



> It sounds like the Ping problem is separate from the FTP problem.


If the problem with not being able to ping or tracert is not connected to the other symptoms I am experiencing what would you suggest? The funny thing is, ping and tracert work in safe mode but not under normal conditions. As I can ping in safe mode my ISP say it must be a problem with Zone Alarm. 

Rich


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## InspectorGadget (May 14, 2005)

Hmmm... we could have a situation here with the ISP service connection going up and down tricking us into thinking it's dependent on other conditions in the PC but it might be a coincidence. I'm suspicious because FTP was not working at that time.

Did you try safe mode right after the failures you listed above? I'm interested in seeing if normal mode/safe mode/normal mode works as expected back to back. Here are a couple of extra test conditions:

1. Would you mind repeating the tests (normal mode, Zone Alarm off, Ping and FTP), and if it fails, immediately boot into safe mode and try again?

2. Would you repeat the tests (normal mode, Zone Alarm off, Ping and FTP) at a time that FTP is actually working?

- The Inspector


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## RDN (May 14, 2008)

Isn't it annoying when right in the middle of finding the cause of a problem, and right after the TechSupport helper has given good advice and clearly wants to sort it out... the OP just (as we say in England) buggers of, without so much as a "by your leave".

Ah well, I will continue searching the web for an answer to my problem.


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