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Isilon CIFS share and NAT/PAT
I have observed in the past that Microsoft's implementation of CIFS share over TCP/IP does not support multiple simultaneous CIFS clients who are NAT/PATted to a single source IP address. When a new client connects to the Win server with that same source IP, any existing client with that source IP has their connection reset. I believe that this limitation is coded on the server-side; I read one blog mentioning that Microsoft's explanation is that this ensures that if a client reboots, the stale CIFS connection is flushed when it reconnects.
Does anyone know if OneFS has incorporated this same "feature" (resetting active TCP flows upon receipt of a new connection on TCP/445)? Or are others successfully serving multiple CIFS clients who appear to Isilon behind a single IP?
joshdfreeman
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Posted June 23rd, 2015 11:00
Hello BradleyUC,
My experience has been that there are a number of environments which use NAT over a WAN and there haven't been any issues with doing this (WAN accelerators notwithstanding) . Myself, I've worked in one environment which had up to 520 users connecting via SMB1 and SMB2 from one NAT'd address without issue.
From a technical perspective, so long as the outgoing TCP ports used by the clients to connect to an SMB server don't illegally overlap, the clients should be able to proceed to a Session Setup and receive a unique SessionID which is then used to manage further communications.
I did find an article, "The case of the mysterious SMB connection resets", in reference to disconnection of all other users over NAT, and this appears to be failing in direct hosting IPs and virtual circuit semantics used only in MS-CIFS, the precursor to MS-SMB.
In searching further, there appears to be a Microsoft KB article on a fix for this issue present in Windows 2000 Service Pack 3, so I wouldn't expect this to be an issue anymore!