Wireshark-users: Re: [Wireshark-users] SMB problems when ICMP is blocked?
From: "John Martin [[email protected]]" <[email protected]>
Date: Fri, 5 Mar 2010 14:58:33 -0500

Short answer:

1)       Yes

2)       I never tried.  We allowed ICMP with the following types-0 (echo request) and 8 (echo reply) and only from certain machines or subnets.  SMB requires ping to go through.  I read something that said as much in SMB documentation some time ago, can’t remember when or what was specifically said.  Don’t know if there is a way to turn it off.  My guess is no. 

 


From: [email protected] [mailto:[email protected]] On Behalf Of Feeny, Michael (GWMT-TASCS)
Sent: Thursday, March 04, 2010 5:25 PM
To: [email protected]
Subject: [Wireshark-users] SMB problems when ICMP is blocked?

 

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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