Note for AirPort: If you have an AirPort base station, it may simplify the troubleshooting procedure to remove it from your network temporarily and set up one computer to connect directly to your DSL or cable modem, using the steps below. After re-establishing service to the computer, see the AirPort section at the end of this document. Alternatively, you may troubleshoot from a more AirPort-specific perspective by seeing the AirPort Troubleshooting Outline. Furthermore, AirPort users should be sure that the setting to connect automatically via PPPoE is not selected for the Built-in Ethernet port on client computers, as described in technical document TS1850, "AirPort: Can Connect to Base Station But Not to Internet When Using PPPoE".
Check modem cables
Verify that all cables related to the modem are plugged in and firmly inserted. This includes the modem's power cord, the cable from the modem to the computer, and the cable from the modem to the wall outlet. To be sure a connection is properly inserted, disconnect and reconnect it. Be sure that cables have not been cut, chewed, or otherwise damaged.
If you have any hubs or routers in use, be sure to check all cables and power supplies. If you have more than one power supply available for a type of hub or router, try swapping the power supplies. A defective power supply may affect network traffic.
Reset/power cycle modem hardware
Cycle the power on your DSL or cable modem by turning it off for a few minutes then turning it back on. Some ISPs recommend that you unplug the modem's power cord. This is required if the modem does not have a power button. If the modem has a reset button, you may try it before or after cycling the power.
Check indicator lights on modem
First, check to see if the DSL or cable modem has a "standby" light or button. Some popular modems may not connect to the Internet when in standby mode. If applicable, be sure the modem is not in standby mode.
Other indicator lights can provide useful information about cabling connections. A light named "Cable" or "Online," for example, indicates whether the ISP's network is available, while a "PC" or "link" light indicates whether the hardware connection between the computer and modem is good. A positive (see Note) link light almost always indicates that the Ethernet ports on each device are working properly, and thus a positive link light makes it very unlikely that an Ethernet port failure is causing the issue.
Note: If the lights on your modem vary only between on and off and do not change color, then a "positive" light is one that is on. If the lights on your modem change color, then green is likely to mean positive.
If your link light is positive, skip to the section, Check System Preferences settings. If there is no link, try modem and Ethernet hardware troubleshooting.
Modem and Ethernet hardware troubleshooting
If a link light remains off after you have checked your cables and cycled the power, you need to re-establish the link before continuing. If your computer included an Apple Hardware Test CD, use it to check for any issue with your hardware. If no problem is found, contact your Internet service provider. They may be able to remotely test whether your modem has failed. If no problem is found with the modem, you should replace the Ethernet cable, since it is the most easily replaced component.
If replacing the Ethernet cable does not establish the link, you will need a third Ethernet device to determine whether the computer or modem is failing to link. The third device could be a simple ("dumb") Ethernet hub with link lights (an inexpensive 10Base-T hub found at any computer store will do), an Ethernet switch with link lights, another computer, a router, or a wireless base station. When using a hub or switch to test, simply connect both the computer and modem to the hub or switch, then check the link lights on the hub or switch to see which of the other devices is not connecting. If you use another computer (Mac or PC) to test, check to see if the other computer has an Ethernet link light (many do not). If there is no link light on the computer, set up a file sharing connection to verify connectivity. If you use a router or base station to verify connectivity, connect as instructed by the device's documentation. If the router or base station has link lights, you may use the simple link light test.
If you are not able to use this type of test, then do whichever of the following is more convenient for you: either exchange your modem with your Internet service provider or take the computer to where its performance can be verified.
Be sure that your software settings are correct, as described in the next section, Check System Preferences settings.
If you still cannot connect, you may have a DNS issue: either that your Internet service provider's DNS service is not working, or that you did not configure it as instructed by them. To make that determination, see technical document TS1843, "Mac OS: Troubleshooting 'A connection failure has occurred', 'The specified server could not be found' or Similar Messages'".
If you still cannot connect and your cable modem link light is positive, then you may be experiencing a relatively uncommon circumstance in which a defective Ethernet cable produces a positive link light. If you have not replaced your Ethernet cable yet prior to this point, you should now substitute a new or known good Ethernet cable for the one you have been using.
Check System Preferences settings
Use the System Preferences application to verify four things: that Built-in Ethernet is your primary network interface, that PPPoE is selected, your account information, and your TCP/IP settings. Follow these steps:
- 1. Choose System Preferences from the Apple menu.
2. Choose Network from the View menu.
3. Choose Active Network Ports from the Show pop-up menu ("Advanced" from the "Configure" pop-up menu prior to Mac OS X 10.1).
4. Be sure that the checkbox for "Built-in Ethernet" is selected.
5. Drag Built-in Ethernet to the top of the Port Configurations list to make it the preferred, or primary, network interface.
6. Choose Built-in Ethernet from the Show pop-up menu.
7. Click the PPPoE tab.
8. Be sure the checkbox for "Connect using PPPoE" is selected.
9. Check the Account Name field to be sure that you have entered the correct information, as obtained from your ISP.
10. If you choose to save your password, try retyping it to be sure that it is correct.
11. Click the TCP/IP tab. Follow your ISP's instructions for setting up this pane. For more information, see technical document HT2301, "Mac OS X: How to Connect to the Internet with PPPoE".
12. If you have made any changes, click Apply Now.
If you have two or more computers attempting to share an Internet connection, be sure that your network is set up properly. You need to know if your ISP provides only one IP address or if it provides multiple IP addresses. If only one IP address is used, then you must have a router capable of connecting via PPPoE and sharing that connection, also known as network address translation (NAT) or "IP masquerading." Check the documentation that came with your router for setup information. Check with the person who set up your network. The AirPort Base Station may be used for this routing function.
Additional steps for AirPort
- 1. After successfully connecting to the Internet with the computer, disconnect the modem from the computer.
2. Unplug power cords for both the modem and the base station.
3. Connect the base station to the modem.
4. Plug the modem back in first, then the base station, and wait for the base station's indicator lights to cycle through their startup routine.
5. Start up a computer, and attempt to connect to the Internet via the base station. If you cannot, then you may use the AirPort Setup Assistant (/Applications/Utilities/) to copy your computer's network setting to the base station. If you have an advanced network setup, you may need to use AirPort Admin Utility instead.
Contact your ISP
If you have not resolved the issue with the above steps, contact your Internet service provider.