Wireshark · Wireshark-users: Re: [Wireshark-users] SMB problems when ICMP is blocked?

[Martin Visser <martinvisser99@xxxxxxxxx>]

I'm not aware of Windows using regular ICMP echos (PINGs) to determine whether a remote host is up or not for the purpose of file sharing. ICMP as connectivity as far as I know would not be required, and would only be a trouble shooting tool.

The fact that you said ICMP was blocked would indicate that there is an intervening firewall. I would be looking at whether that is configured appropriately , as far as session idle time and so on.

Also as this is a Wireshark list, you should be using the tool to help research the problem. Look for unexpected RST or FIN packets coming from the server - RSTs might be coming from the firewall. 

Also if the intervening firewall is in fact a HA pair, there may be an issue where an active session on one of the pair is not being passed over to the other, resulting in a dropped session.


Regards, Martin

MartinVisser99@xxxxxxxxx

On Fri, Mar 5, 2010 at 9:25 AM, Feeny, Michael (GWMT-TASCS) <michael_feeny@xxxxxx> wrote:

Hello,

 

I’m troubleshooting a problem where a Windows XP user has problems with a certain mapped drive (file share).  Specifically, after mapping, a file copy from the mapped drive fails, after 10-15 seconds, with a ““The specified network name is no longer available” message.

 

As I have dug into this, I was told that ICMP has been blocked between the user’s site and the site of the remote  file share.

 

Then, after capturing packets, I found that, in addition to the SMB packets between the 2 endpoints, the user’s workstation was sending PINGs to the remote site.  Due to the blocking of ICMP these PINGs are never answered.

 

My suspicion is that, when the PINGs are unanswered, the file system decides that the remote file share host is unavailable, and the file copy is terminated.  (In reality, the file copy seemed to be proceeding just fine.)

 

So…  My questions are…

 

1)      Has anyone else run into this?

2)      Assuming that allowing ICMP between these sites is not an option, does anyone know if one can disable this PING mechanism, so that file sharing operations can proceed successfully?

 

Thx,

Michael

 

Michael Feeny
Bank of America / Merrill Lynch

Global Wealth Management Technology
Technology Architecture, Strategy & Core Services

Application Infrastructure Services

Office: 609-274-2761
Mobile:  484-995-1745
AOL IM: feenyman99

 

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