A dropped Wi-Fi connection in OS X is one of the long-standing frustrations that some Mac users have had to deal with. In some instances a system that works well on one Wi-Fi network will not maintain a connection with another one, and in other instances two seemingly identical Macs (same model and OS version) will result in one connecting to a network and the other not.
These frustrations can be tricky to deal with, and generally the troubleshooting steps revolve around checking the router for any special services, using the older 2.4GHz frequency (802.11 "b" or "g") instead of the 5GHz frequency, and clearing out some of the wireless network configuration options in OS X. Unfortunately there are many factors that can prevent a wireless connection, so many times you end up guessing at the approaches to fixing the problem.
If other computers on the network are connecting just fine (especially if they are Macs), then leave the router alone; however, if multiple systems are not able to connect, then try some options for troubleshooting the router's configuration.
The first thing you should try for your router is to power cycle it. Turn it off for a few seconds and then turn it back on, and see if a simple reset like this is all that is needed (many times it is, and many times this is an overlooked step).
Beyond a reset, try simplifying the router's setup. Many routers have multiple services and radios in them for different connection options, which may result in odd connection behaviors for some devices if they are all enabled:
- Use only one radio
If your router is a dual-band router, then try either the 5GHz radio or the 2.4GHz radio independently to see if you have better luck maintaining the connection.
- Disable repeating functions
If you use multiple routers to bridge Wi-Fi networks and expand your Wi-Fi coverage, try disabling this function and use only one main router to see if you can get the system connected.
- Disable advanced wireless security options
Many routers contain Wi-Fi isolation modes and other options to filter how systems can either connect to the network or access network services, so try disabling these. Some of these like isolation modes are specific to a particular band (2.4GHz or 5GHz), but there are other options like MAC address filtering (options for only allowing specific computers to connect) that are more general for the router.
- Disable optional router services.
In addition to security and access filters, routers have options like file servers for networked folders, printer servers, VPNs, QoS options for prioritizing network activity, and traffic meters. While these should not interact with your system's ability to connect to the router, corruption in their configurations may result in the router dropping the connection.
- Change the authentication scheme
Most modern routers come with options for old WEP passwords in addition to various WPA and WPA2 passwords. Try all of these options independently since authentication problems can result in a dropped connection. If your router supports an Enterprise version of WPA or WPA2, then avoid using this as it may require advanced options like an authentication server (RADIUS server bound to a directory service).
If you are using OS X Server's RADIUS service to manage your Wi-Fi router, then try temporarily disabling this feature and using a standard WPA or WPA2 password, since this will help determine if the problem is with the server's authentication or with the router's ability to handle the connection.
While security options are always recommended, one option for troubleshooting the device is to set the authentication mode to "None" so no password is required. If the system is able to connect properly at this point then you know the authentication scheme is the root of the issue (use this only for troubleshooting, and do not leave your router without either WPA or WPA2 authentication enabled).
- Setup defaults
As a last resort, consult your router's manual and fully reset the device back to factory defaults (this is different from a basic power cycle). Many routers have advanced options for things like fragmentation lengths, preamble modes, CTS/RTS thresholds, and other cryptic looking options that network administrators can use to fine-tune their networks. Generally the default settings for these options should be fine for most home network uses, so consult your manual and reset your router so they will be at their defaults.
- Firmware upgrades?
If your router is a few years old, you can look into whether a firmware upgrade is available for it. Firmware controls how the router's hardware is managed, and updates to it can enable hardware features that were left dormant because they were not yet fully tested, or fix bugs with the current hardware setup. Many routers have a built-in update checking routine, but others will require you to download updates from the manufacturer and load them manually. Consult with your router's manufacturer to see if an update is available for your router.
Besides the router, the only other device in the network setup is your computer and its Wi-Fi connection. Unfortunately unlike the router, you cannot easily just reset the system to some factory default without reinstalling the OS, but there are some options you can try for clearing settings and getting the system connected.
The first step when looking at your system is to try someto see if the behavior can be isolated to certain boot or user account environments (safe mode, an alternate user account, etc.). While the steps in my suggestions should not affect the behavior of Wi-Fi connections, you can also try them to see if they will help.
In addition to troubleshooting steps, you can try removing login items for your account (especially if other accounts on the system are able to connect properly), and try resetting some network-related system services. One of these is the system firewall, so go to the Security system preferences and turn off the firewall temporarily to see if this allows the connection to the router to be maintained. Additionally, try restarting Apple's Bonjour networking service by opening Activity Monitor, selecting the process mDNSResponder and then clicking "Force Quit."
The next step is to take a look at the Network system preferences and clear your Wi-Fi settings in there. The easiest way to do this is to create a new network location so your settings will be stored in a new configuration, though you can also clear your current network configuration or create a new one and delete the old ones. To do this, in the Network system preferences select "Edit Locations" in the location menu, add and name a new location, and then remove the rest.
After you have created a new location, set the port priority to ensure that the system tries to only use the desired network ports. The new location will show your available network ports in the connection list, so click the little gear menu at the bottom of this list and choose "Set Service Order." In here, drag Wi-Fi to the top of the list, and click OK to save the changes.
After doing this, you can optionally disable ports like FireWire or Bluetooth if you do not use these (most people use Wi-Fi or Ethernet), by clicking them individually and choosing "Make Service Inactive" from the same gear menu.
The last option for your computer is to try completely resetting the network configuration. Apple provides a way to do this for the printing system which is exceptionally useful for troubleshooting printing problems, but it does not provide this for other services.
To reset the network configuration in OS X, go to the /Macintosh HD/Library/Preferences/SystemConfiguration/ folder and remove the following files:
After these files are removed, restart the system and then set up your network configuration in the System Preferences again.