--- title: "Mac can't connect to NAS or SMB share after update: fixes · Kilobat Guides" url: "https://kilobat.app/guides/smb-nas-not-connecting-mac" description: "Finder cannot connect to a NAS or Windows share after a macOS update. Connect by IP address, test port 445, check the NAS SMB settings and Local Network access." --- # The Mac cannot connect to a NAS or SMB share Finder connects to SMB shares with an address such as smb://192.168.1.20/share. Test the address, the port and the NAS settings before you change files on the Mac. **Fix this with your agent**Copies a prompt for Claude Code, Codex or any agent that can use Terminal. My Mac has this problem: The Mac cannot connect to a NAS or SMB share. Read https://kilobat.app/guides/smb-nas-not-connecting-mac.md and work through it with me. Install the Kilobat CLI if it’s missing: brew install seifip/kilobat/kilobat. Run the guide’s Terminal and kilobat checks yourself and tell me what you find. List the steps only I can do. Ask before you change any setting. Applies to: Current macOS versions. Local Network access for apps is in macOS 15 Sequoia and later. · Checked: 7 November 2026 ## Symptoms - Finder shows that there was a problem connecting to the server. - The NAS does not appear under Network in the Finder sidebar. - The share connects by IP address but not by name. - One app cannot reach the NAS, but Finder can. - A share that worked before a macOS update does not connect now. ## Likely causes - **The name does not resolve.** Apple says that you may need the DNS name or IP address of the server, not its computer name. - **The server is off or on another network.** For Windows (SMB/CIFS) servers, Apple says to make sure that the server is on the same local network. - **A firewall on the server.** Apple says that you may not be able to connect when a Windows server has its firewall on. - **The NAS settings.** The SMB service, the allowed SMB versions and the user's access are set on the NAS. - **An old nsmb.conf file.** Settings in /etc/nsmb.conf apply to every SMB connection from the Mac. - **Local Network access is off for an app.** On macOS 15 and later, an app needs Local Network access to reach the NAS. ## How to check 1. In the Finder, choose Go > Connect to Server. 2. Enter the address with the IP address, such as smb://192.168.1.20/share. Click Connect. 3. If the IP address works and the name does not, the name lookup is the problem. 4. Test whether the NAS accepts connections on port 445. ``` nc -vz -G 5 192.168.1.20 445 ``` 5. Look for SMB servers that advertise with Bonjour. Press Control-C to stop. ``` dns-sd -B _smb._tcp ``` 6. Show the SMB version and signing of shares that are mounted now. ``` smbutil statshares -a ``` 7. Find out if an nsmb.conf file exists. If it exists, show its settings. ``` cat /etc/nsmb.conf ~/Library/Preferences/nsmb.conf ``` ## How to fix it 1. Use the IP address in Connect to Server. Give the NAS a fixed address in the router. 2. In Finder > Settings > General and Sidebar, select Connected servers. 3. In the NAS settings, make sure that the SMB service is on. 4. Make sure that the NAS allows SMB2 or SMB3. Use the NAS maker's documentation for the menu. 5. Synology says that the DSM minimum SMB version cannot be SMB3, as older SMB3 clients would fail. 6. Make sure that your user has access to the share on the NAS. 7. If a third-party app cannot reach the NAS, open System Settings > Privacy & Security > Local Network. 8. Turn on the switch for the app. Then quit the app and open it again. 9. If you find an nsmb.conf file that you do not need, ask who added it before you remove it. 10. Users report that nsmb.conf changes help after some updates. Apple does not document them for current macOS. ## With Kilobat 1. Test the TCP connection to port 445. Read the IPv4 line. It says connected, refused or no answer. ``` kilobat why 192.168.1.20:445 ``` 2. The check then tries a secure web connection. SMB does not use it, so ignore that step. 3. Find SMB servers that advertise with Bonjour. ``` kilobat bonjour _smb._tcp ``` 4. List the devices that the Mac talked to recently. Look for the NAS and its address. ``` kilobat devices --bonjour ``` 5. Check whether devices on this network can see each other. Some guest networks isolate them. ``` kilobat local check ``` 6. Show whether a VPN is on. Turn it off for a test if the NAS is on your local network. ``` kilobat vpn ``` ## Questions **What does Apple say about SMB signing?** Apple's archived article says that signing is off by default in macOS 10.13.4 and later. It turns on when the server offers it. **Should I turn off signing in nsmb.conf?** Apple's steps are for macOS 10.13.3 and earlier. Apple warns that this lowers the security of the SMB connection. **Which port does SMB use?** Apple's port list shows TCP 445 for SMB, and TCP 139 for SMB over NetBIOS. **Which SMB versions does the Mac use?** The nsmb.conf man page in macOS 27.2 lists SMB 1, 2 and 3 as enabled by default. ## Sources - [Apple Support: Connect your Mac to shared computers and servers](https://support.apple.com/guide/mac-help/connect-mac-shared-computers-servers-mchlp1140/mac) - [Apple Support: Servers and shared computers you can connect to on Mac](https://support.apple.com/guide/mac-help/servers-shared-computers-connect-mac-mchlp3015/mac) - [Apple Support: If your Mac can't connect to another computer](https://support.apple.com/guide/mac-help/if-your-mac-cant-connect-to-another-computer-mchlp1656/mac) - [Apple Support: Turn off packet signing for SMB 2 and SMB 3 connections (archived)](https://support.apple.com/en-us/101442) - [Apple Support: TCP and UDP ports used by Apple software products](https://support.apple.com/en-us/103229) - [Apple Support: Control access to your local network on Mac](https://support.apple.com/guide/mac-help/control-access-to-your-local-network-mchla4f49138/mac) - [Synology: DSM 7.4 File Services & Protocols](https://www.synology.com/en-global/dsm/7.4/software_spec/file_services_protocols) - nsmb.conf(5), smbutil(1), dns-sd(1) and nc(1), man pages installed with macOS 27.2 Checked on 7 November 2026. ## Related guides - [An app cannot find devices on the local network](https://kilobat.app/guides/local-network-permission): macOS 15 Sequoia and later ask before an app connects to devices on your local network. - [Find the devices on your local network from a Mac](https://kilobat.app/guides/find-devices-on-network): macOS has two built-in ways to see other devices: the ARP table and Bonjour. - [Screen Sharing cannot connect to another Mac](https://kilobat.app/guides/screen-sharing-not-connecting-mac): The other Mac must have Screen Sharing on and allow your user. - [The macOS firewall blocks incoming connections](https://kilobat.app/guides/macos-firewall-incoming): The macOS firewall controls connections that other computers start to your Mac.