Carlton Chin

Q: Wifi works but Ethernet does not

I just switched ISP. I am using RCN's cable modem which is the same one that Xfinity uses. I am also using a Linkysys EA4500 router. I had no problems with the set-up yesterday before they changed it over this morning.

 

I have two iMacs (myself and my wife). If the cable modem is directly connect to either of the two iMacs, the internet works fine. However, when the Linksys router is part of the configuration, my wife's iMac can connect via Ethernet port but my iMac will not. My iMac can connect via WiFi. However, it will no connect if I use an Ethernet cable.

 

I have already reset the router to factory setting and reboot by iMac and clear the PRAM, swapped out Ethernet cables. What's going on here?

iMac, OS X Mountain Lion (10.8.5), null

Posted on Jul 23, 2016 8:05 AM

Close

Q: Wifi works but Ethernet does not

  • All replies
  • Helpful answers

  • by John Galt,

    John Galt John Galt Jul 23, 2016 9:27 AM in response to Carlton Chin
    Level 8 (49,039 points)
    Mac OS X
    Jul 23, 2016 9:27 AM in response to Carlton Chin

    The problem you describe will occur when changing the device connected to a cable modem without restarting the cable modem. Cable modems that are not also routers will communicate with one and only one device, and will refuse to connect to anything else until you cycle its power.

     

    Power down your RCN cable modem and leave it powered down. For reasons I do not understand (and which may not be required), some cable ISPs also recommend physically disconnecting their coaxial cable from the modem to effect a "full reset". During that time you might as well power down the Linksys router also. Connect the iMacs to the router, either directly to its LAN ports, or through an Ethernet switch. It's not necessary to power down the Macs.

     

    Wait a moment or two, then reconnect the cable to the modem if you disconnected it, and power up both the modem and the router. That should work.

  • by Carlton Chin,

    Carlton Chin Carlton Chin Jul 23, 2016 10:57 AM in response to John Galt
    Level 3 (823 points)
    Desktops
    Jul 23, 2016 10:57 AM in response to John Galt

    I already tried those steps. My wife's iMac will connect to the Internet just fine. It can connect to the WiFi fine without the Ethernet cable. It can connect with just the cable with the WiFi off. When both WiFi is on and the Ethernet cable is attached, the connection works fine. However, when I have WiFi on and I attached the Ethernet cable, the connection freezes or blocks the WiFi and the browser window will display the "Safari Can't Find the Server" message. Once I disconnect the cable the it connects fine via WiFi. I even checked to make sure the FireWall is not active on my iMac and even changed the router IP to see if it would make the least bit of difference. Any other suggestions?

  • by John Galt,

    John Galt John Galt Jul 23, 2016 11:10 AM in response to Carlton Chin
    Level 8 (49,039 points)
    Mac OS X
    Jul 23, 2016 11:10 AM in response to Carlton Chin

    It is advantageous to leave Wi-Fi "on" even though you want to give Ethernet precedence, so leave it that way. For example, Wi-Fi is required for AirDrop to work even if you're using Ethernet for your LAN.

     

    In System Preferences > Network, click the "gear" icon > Set Service Order...

     

    Drag Ethernet above Wi-Fi if it is not already configured that way.


    OK then Apply.

     

    Does that help?

     

    If not: return to System Preferences > Network, select the Ethernet interface, and click Advanced...

     

    Click the Proxies tab and confirm that nothing is checked under "Select a protocol to configure".

     

    Then, click the Hardware tab and describe the entries for Configure, Speed, Duplex, and MTU.

     

    Click Cancel when you're done.

  • by Baby Boomer (USofA),Solvedanswer

    Baby Boomer (USofA) Baby Boomer (USofA) Jul 23, 2016 4:33 PM in response to Carlton Chin
    Level 9 (57,623 points)
    Jul 23, 2016 4:33 PM in response to Carlton Chin

    Try the following:

     

    System Preferences>Network

    Click the Assist Me button.

    In the next window that pops up, click the Diagnostic button & do the necessary.

    ===============

    Ethernet troubleshooting

    Trash the following plist files by going to Macintosh HD>Library>Preferences>SystemConfiguration

     

    com.apple.airport.preferences

     

    preferences

     

    NetworkInterfaces


    Repair permissions and restart your computer.  Empty the trash. 

    Afterwards try John Galt's suggestion again if you are still experiencing ethernet problems.


    =========


    If you have AppleCare, give them a call & let them deal w/it.  You are entitled to onsite service since you have a desktop.

    Out of warranty, lug your iMac to your local Apple Store or an APSP.

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

    ezgif.com-resize.gif

  • by Carlton Chin,

    Carlton Chin Carlton Chin Jul 23, 2016 4:34 PM in response to Baby Boomer (USofA)
    Level 3 (823 points)
    Desktops
    Jul 23, 2016 4:34 PM in response to Baby Boomer (USofA)

    Thanks! When I ran the diagnostic, it immediately fixed the problem.

  • by Baby Boomer (USofA),

    Baby Boomer (USofA) Baby Boomer (USofA) Jul 25, 2016 1:07 PM in response to Carlton Chin
    Level 9 (57,623 points)
    Jul 25, 2016 1:07 PM in response to Carlton Chin

    You're welcome & good luck.

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

    ezgif.com-resize.gif