Shulou(Shulou.com)06/02 Report--

Windows accesses the shared folder using the smb protocol, which defaults to port 139,445. the company's office network does not know why the policy is set not to allow the use of port 445. therefore, port 139 is usually used to access the share.

The funny thing is that sometimes some office computers cannot access sharing, and there is no problem with the inspection services: Server, Workstation, Computer Browser, file sharing and printer sharing in Microsoft network, firewall is turned off, NetBIOS settings are turned on, but they cannot be accessed.

Check the access port and find that this computer only connects to the server's port 445. it is strange that why not go to port 139. the default should be: if the client enables NetBIOS, both port 139 and port 445will be accessed when connecting. If you get a response from port 445, the client will send RST to port 139to terminate the connection, and then SMB from port 445. if you don't get a response from port 445, Instead, get a response from 139, so talk from port 139. I have opened the NetBIOS agreement, why not take effect?

After the final investigation, it turned out that it was caused by the duplicate name of the computer. When SMB uses NetBIOS to establish a connection with port 139, it will check whether there is a duplicate name in the local network. If there is a duplicate name, only port 445 will be used to prevent conflicts.

I see, so it is normal after changing the name of the computer.

In fact, the main reason is that this computer does not have a domain, and if you add a domain, there will not be such a problem; and a computer with a duplicate name cannot add a domain, and you must change the computer name and restart before you can add a domain.

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