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If I want to allow Windows networked drives between two firewalled computers, do I need to open ports 137-139, or is port 445 sufficient? I have to submit a form and get approval to open firewall ports, and I don't want to ask for more open ports than I need. All of the machines here are Windows XP or later.

Note: when I say "Windows networked drives", I'm not entirely sure whether I'm referring to SMB or CIFS, and I'm not entirely clear on the difference between the two protocols.

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up vote 22 down vote accepted

Ports 137-139 are for NetBios/Name resolution. Without it you will have to access machines by IP address opposed to NetBIOS name. Example \\\share_name opposed to \\my_file_server\share_name

So port 445 is sufficient if you can work with IP addresses only.

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At my site, NetBIOS names are always the same as DNS names. So if I refer to machines by hostname, will Windows be able find the machine through DNS without using NetBIOS? – Jonathan Jan 3 '12 at 17:28
As long as you have functioning DNS available to the client it should suffice. – Tim Jan 3 '12 at 18:45
does this also work with public IP addresses? Is it enough to open port 445 in the firewall of the ADSL modem/router? – Hrqls Feb 18 '15 at 9:33

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