Can I use a second Airport Extreme Base station to use Home sharing a. use the ethernet input to extend my internet in a back room?

I'm going to take a chance and guess that you will be using a Mac to set up the AirPort Extreme.

Temporarily, move the AirPort Extreme to the same room or close proximity to the Time Capsule

Power up the AirPort Extreme and let it run for a minute or two

Hold in the reset button on the back of the Extreme for 7-8 seconds, then release

Allow a full minute for the Extreme to restart to a slow, blinking amber light status

Click the WiFi menu at the top of the Mac's screen

Look for a listing of New AirPort Base Station

Just under that heading, click directly on AirPort Extreme

When you click directly on AirPort Extreme, that will start up the setup "helper" or "wizard". The wizard will take a few seconds to analyze the network and then display a screen that looks like the example below, except that you will see an AirPort Extreme displayed along with the name of your wireless network

Next to Base Station Name, type in a short simple device name for the AirPort Extreme

Click Next

The next window that appears will confirm that the AirPort Extreme is being configured to wirelessly extend the name of the network that the Time Capsule is providing.

When you see the message appear in the next window of Setup Complete, click Done

Power off the AirPort Extreme

Locate the AirPort Extreme where it will be needed. Ideally, you will have line-of-sight between the Airport Extreme and Time Capsule, since the WiFi signal degrades rapidly with distance and any obstructions like walls or furniture that the WiFi signal must pass through to reach the AirPort Extreme

Power up the AirPort Extreme and wait for a green light, which will indicate that the WiFi signal is strong enough for the AirPort Extreme to connect

Connect any Ethernet devices to a LAN <--> Ethernet port on the back of the AirPort Extreme. If the device has WiFi capability, be sure to turn off the WiFi on the device so that the connection will occur over the wired Ethernet connection.

WiFi devices in close proximity to the AirPort Extreme will connect to the WiFi signal that the Extreme is providing. Unfortunately, this will be a much slower WiFi signal than the Time Capsule is providing to devices that are near the Time Capsule.

If you want to use an iPhone or iPad to set up the AirPort Extreme.......

Go to the Home Screen on the iPhone / iPad

Tap on Settings

Tap on WiFi

Look for a listing of New AirPort Base Station

Tap on AirPort Extreme

The setup is similar to the setup listed above

After a time, the amber light on the AirPort Extreme might begin to slowly blink. If this occurs, this is likely a message that newer firmware is available for the AirPort Extreme.

Post back for more instructions on how to update the firmware

You will be connecting the A1301 Extreme back to the "main" Extreme using a permanent wired Ethernet cable connection, correct?

If you were planning to use WiFi, the performance would be no different than what you have now connecting the MacPro using WiFi. Yes, you will pick up the Ethernet ports, but since the speed of the old Extreme will be limited to the speed of the WiFi connection back to the main AirPort Extreme, there will be no advantage to connecting the MacPro using Ethernet.

Maybe another way to say the same thing........there is no speed "boost" when you extend the network using a WiFi connection. There is a speed loss. This is why you would want to use Ethernet to connect the old Extreme back to the main AirPort Extreme. There is no speed loss through the Ethernet connection.

If you have reset the old AirPort Extreme, you must first reconfigure it again to connect to the network. It won't automatically configure itself and display a green light.

The second reason was to plug in my back-room iMac into that second extreme by Ethernet cable

to get a better than WIFI only internet.

Sorry, but it won't get "a better than WiFi only Internet" signal.

As we already explained above, the signal provided by the remote Extreme (no matter whether it is WiFi or Ethernet) will be no better than the quality and speed of the WiFi signal that the Extreme receives from the Time Capsule.

That is why we were hoping that you were planning to connect the Extreme back to the Time Capsule using a permanent wired Ethernet cable connection.

If you need additional Ethernet ports to connect other Ethernet devices to the AirPort Extreme, that would be a reason to consider adding the Extreme, even though the signal will not improve. Or, simply putting the Extreme to use would be another, even though its addition to the network will not improve the signal at all.

In the meantime I don’t even get the second extreme to go to green in my backroom!

If you decide that you want to use the Extreme, and the Extreme is operating normally and the setup is correct, the Extreme will be working correctly. Do you need some help with the setup of the Extreme?

I was thinking to use it as a WIFI extender since there are a couple of walls and some distance from the main Extreme.

Shouldn't it work like an Airport express?

The Extreme can certainly be used as a WiFi extender, but like the Express, it can only "extend" or "repeat" the speed and quality of signal that it receives. We have tried to explain this several times, but do not seem to be getting this message through to you.

Like the Express, the Ethernet ports can also be used to connect Ethernet devices, but here again, the speed at the Ethernet ports on the Extreme will only be as fast as the wireless signal that the Extreme receives from the Time Capsule.

The Extreme cannot "boost" the speed of the wireless connection that it receives from the Time Capsule and neither can the Ethernet ports on the Extreme. I don't know how to explain this any other way than provide the facts to you.

Now, if you have some devices that cannot connect using WiFi, then it would make sense to add the Extreme to the network so that you can connect those devices to an Ethernet port on the Extreme. The signal will not be any faster this way, but at least the devices will be able to connect to the network. And, other WiFi devices in the area will able to connect to the Extreme.

Will you be using the iMac to set up the AirPort Extreme or another Mac? Or, will you be using an iPhone or iPad? We ask because the setup is different depending on what device that you will be using.

Power off the Time Capsule (main AirPort Extreme)

Restart the Mac

Power the Time Capsule (AirPort Extreme) back up and let it run for a few minutes

Start over again from the beginning with the setup of the older AirPort Extreme

If the "unexpected error" appears again, use an iPhone or iPad to set up the older AirPort Extreme from the beginning

If the error occurs again, something is wrong with the older AirPort Extreme. Nothing we can do about that unfortunately other than keep trying.

As luck would have it, I have an old A1301 AirPort Extreme here that I haven't used in many years, but it connected just fine to my "tower" version of the AirPort Extreme and Time Capsule when I tested it out.