Today I tried to access a Windows shared folder from my Mac over the local network by entering smb://192.168.0.x in Finder's "Connect to Server", but the connection kept failing. After some quick troubleshooting, I found the root causes and fixed them. Here's the key process.

Initial Investigation

First, I checked the SMB service status on the Windows side and verified that port 445 (responsible for SMB communication) was listening normally. The service itself was running fine, which meant the problem was in the network and firewall settings.

Problem 1: Home LAN Classified as Public Network by Windows

For security, Windows blocks file sharing on public networks by default — the firewall automatically blocks inbound connections on port 445. This makes sense in public places, but it prevents normal file transfers on a home LAN and was the primary cause of the connection failure.

Problem 2: Windows Firewall SMB Sharing Rules Mostly Disabled

The built-in SMB firewall rules were mostly disabled. The few that were enabled only allowed specific IPs, not the entire local subnet, preventing the Mac from establishing a connection.

Fix Steps

Step 1: Change Network Type from Public to Private

Open PowerShell as Administrator and run the following command to reclassify the network as Private, allowing Windows to trust the local network and unblock file sharing:

Set-NetConnectionProfile -InterfaceAlias "Ethernet" -NetworkCategory Private

Step 2: Add a Dedicated Firewall Rule to Allow Port 445

Rather than modifying the existing built-in SMB rules (which have complex interdependencies and are partially disabled), it's cleaner to create a new dedicated inbound rule that reliably opens TCP port 445:

New-NetFirewallRule -DisplayName "SMB-Allow-LAN" -Direction Inbound -Protocol TCP -LocalPort 445 -Action Allow -Profile Private

After applying these changes, the Mac connected successfully and could access the Windows shared folder.

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Key Takeaways

1. LAN file sharing requires Windows network set to Private — Public network completely blocks sharing.
2. SMB relies on port 445 — even if the service is running, a firewall block means no connection.
3. Create a dedicated firewall rule instead of modifying built-in rules — simpler, more reliable, and easier to manage or remove later.
4. Just use the username to connect — no need to prepend the computer name in the connection settings.