MacBook Air with USB Network Adapter: No Connection
Today I had the opportunity to waste a bunch of time trying to track down a particularly frustrating problem. I had a faculty member's machine whose USB network adapter (official Apple one) would not show any connection when plugged into his port in the wall. I first tried a new cable to the port, then a second port in his office, then a second port on the switch, all to no avail.
I then thought that the problem must be the computer or adapter itself. So, I grabbed my MacBook air to test, but with the same results. So, it is the adapter right? I grabbed a second adapter and ran it over with my MacBook to find that it still wouldn't work on either machine with either port in his office.
So, I then take my macbook to his the office where I borrowed the extra USB network adapter to find that my machine wouldn't work with either adapter in that office, but the professors machine in that office (another MacBook Air) would work with both of them. I then feel like a total failure and come back to my office where I plug in to a cord from my MacPro and it comes right up and works. Plug into a hub and it works. Plug into a Cisco switch and it works.
The only difference between these two MacBook Airs' that won't work and the one that will is that mine is 10.8, the other that won't work is 10.7, and the one that will is 10.6.
***Let it be noted that, originally, the speed and duplex were manually specified on the port configuration and the MacBook Airs were auto-negotiating. I also tried manually specifying the settings (100 Mb/s Half Duplex) on the Airs to no avail.
SOLUTION:
Turns out that, at least on a Cisco switch with these two laptops, I had to set both the USB network adapter interface AND the port on the switch to Auto-negotiate. Here are the steps to do that on the MacBook Air:
1.) Go to Apple icon in upper left corner and then "System Preferences".
I then thought that the problem must be the computer or adapter itself. So, I grabbed my MacBook air to test, but with the same results. So, it is the adapter right? I grabbed a second adapter and ran it over with my MacBook to find that it still wouldn't work on either machine with either port in his office.
So, I then take my macbook to his the office where I borrowed the extra USB network adapter to find that my machine wouldn't work with either adapter in that office, but the professors machine in that office (another MacBook Air) would work with both of them. I then feel like a total failure and come back to my office where I plug in to a cord from my MacPro and it comes right up and works. Plug into a hub and it works. Plug into a Cisco switch and it works.
The only difference between these two MacBook Airs' that won't work and the one that will is that mine is 10.8, the other that won't work is 10.7, and the one that will is 10.6.
***Let it be noted that, originally, the speed and duplex were manually specified on the port configuration and the MacBook Airs were auto-negotiating. I also tried manually specifying the settings (100 Mb/s Half Duplex) on the Airs to no avail.
SOLUTION:
Turns out that, at least on a Cisco switch with these two laptops, I had to set both the USB network adapter interface AND the port on the switch to Auto-negotiate. Here are the steps to do that on the MacBook Air:
1.) Go to Apple icon in upper left corner and then "System Preferences".
2.) Then go to the "Network" preference pain
3.) Choose the USB network adapter and then click on "Advanced"
4.) Go to the "Hardware" tab and select "Automatically" from the "Configure" drop down and choose OK and Apply.
5.) If you are working with Cisco switches, hopefully you already know how to set a port to Auto-negotiate. Suffice it to say, the following commands would get you there:
Connect to your switch
en
conf t
int fa0/## Where ## is the port number you want to configure
no speed
no duplex
hit ctl and z
write to save changes
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