A process of elimination can help you determine the cause behind an intermittent Internet connection affecting your Mac. This includes testing another computer, tablet or smartphone on the network to see if the issue affects all of your technology. If you experience connection issues across multiple devices, then your router, modem or Internet service provider may be the issue. If the issue occurs only with your Mac, then you might need to change some system settings and repair permissions.

Hardware Issues

If multiple users are unable to connect to your Wi-Fi, there might be an issue with your hardware setup. First, check all cables to make sure that they're plugged in tightly. Next, check the power light on both the router and modem to make sure they're powered on. If the cables and power are good, unplug both the modem and router to power them down and then plug them back in to restart them. Wait a few minutes for the network to become available again and attempt to connect. If you're using an Ethernet cable to connect your Mac to the Internet, use a new cable.

ISP Outages

When there doesn't seem to be an issue with your hardware setup, then call your ISP to see if there's any reported downtime for your area. Find the customer service phone number to check in about local outages. Some providers can run remote diagnostics and test your connection to see if they can isolate the issue. If there's a problem with your building's cable configuration, they may send a repair technician on-site to fix the problem.

OS Settings

If you're experiencing Internet issues only on your Mac, old passwords and cached settings may prevent you from logging onto a network. Launch System Preferences and then click on "Network." If you're having Wi-Fi issues, click on "Advanced," open the "Wi-Fi" tab, select the network name, and click on the "-" symbol to remove it from the Preferred Network list. You can remove old passwords by launching "Keychain Access," clicking on "System" and deleting any passwords associated with the Wi-Fi network you're trying to connect to. Next, click on your Wi-Fi menu, select the network, and type in the password. Your Mac will attempt to connect to the network again.

Disk Permissions

Broken permissions associated with your Airport's functions can also cause unpredictable Internet issues. You can fix this with Disk Utility. Open Launchpad from the dock to see all of your applications. Visit the "Other" folder and click on the "Disk Utility" app. Select your Mac hard drive from the list. Click on "Repair Disk" and allow the process to run. Once it's complete, restart the computer and attempt to connect to the network again.