Airport Express Extending a Network via Ethernet

Check the settings under the wireless tab using AirPort Utility for the AirPort Express.

If the setting is "Extend a wireless network"........that setting is used only if the Express is connecting to the Time Capsule using wireless. If you try to connect an Ethernet cable using this same setting, the Express portion of the network will crash due to a huge feedback loop.

An Ethernet connection requires a different setting on the Express, which the AirPort Utility "wizard" will automatically configure correctly if you start over and reset the Express, make the Ethernet connection, then run the AirPort Utility setup "wizard".

Hint......the AirPort Express will be set up to "extend using Ethernet" by the setup wizard, but the actual setting that is applied may surprise you if you check the settings on the Express once it is up and running correctly.

Here is an example of an AirPort Express that is being set up to extend using Ethernet with an AirPort Extreme:

If you are not clear on this, post back and we'll go over a step by step setup with you.

When you connect a base station by Ethernet to another for the purpose of extending the wireless range, be sure to configure the Express to "Create a wireless network," and not to "Extend a wireless network." The latter setting is only when the connection between base station will be wireless. Is this what you set it for?

Basically, you are creating a roaming-type network with your base stations.

If you assume that the Ethernet cable is good and If you are sure that you are making the Ethernet connection......before......you attempt to set up the Express and the Ethernet cable is connected to the WAN "O" port on the Express, then you very likely have a bad Ethernet port on the Express.

Extremely unlikely that you would have two bad versions of AirPort Utility.....on both a Mac and iOS device. In 10+ years on the forum, I have never seen a report of an AirPort Utility issue on both a Mac and iOS device. Try another Mac or iPhone / iPad if you have one handy, but I will be amazed if that helps.

Take the Express in to an Apple Store if you have one near you and ask them to check the Ethernet port.

Shot in the dark........

Try powering off the Time Capsule for a few minutes, then power it back up.

Then, start over and try to set up the Express again.

Check the Ethernet ports on the Time Capsule. Does the small green light come on next to the Ethernet port on the Time Capsule when you connect the Express using the Ethernet cable?

If not, the Ethernet port on the Time Capsule has failed. Sometimes, all 3 fail at the same time.

Do you have an iPhone or iPad?

Still not sure how you tested the Ethernet cable. If you connected a computer to test, only 4 of the 8 conductors or contacts need to be working for a connection to occur. So, the Mac will work fine with a bad connection.....but the Express won't.

The AirPort Express requires that all 8 contacts are working correctly. Try another cable if you have one handy as a test.

I can't find any fault with Mojave on two different Macs that I have checked here, and there are no other reports of Mojave / AirPort Utility setup problems that I can find on a forum search.

Still would be a good idea to try an iPhone or iPad for the setup if you have one.

Any change in things with a different Ethernet cable?

Shot in the dark........

Try powering off the Time Capsule for a few minutes, then power it back up.

Then, start over and try to set up the Express again.

Then you know that you either have a bad Ethernet cable or a bad Express.

9 times out of 10 problems like this are a bad cable or poor connection(s) with the plugs and ports.

Anything is possible. I simply cannot duplicate the issue that you are reporting nor can I find any other similar reports on this forum. Perhaps another user can help.

I do notice that once it extends the network, the "Internet" icon on the AirPort Utility goes amber and it shows disconnected. When the network is extended, the Internet seems to come and go. Is that normal?

I assume that you are asking about the Express extending using wireless, not Ethernet.

Not normal. You should have a solid green light with either a wireless or wired connection.

iPad or iPhone handy?