airport extreme

Unfortunately, it appears that you did not follow the instructions that I provided to let the AirPort Utility "wizard" set up the extending AirPort Extreme for you.. If you had done this, the extending AirPort Extreme would have been set up literally automatically and correctly. The only "active" thing that you need to do is assign a device name that you want to call the AirPort Extreme.

Let's review the same steps again as provided above, but I have added some additional comments.

Connect an Ethernet cable from one of the 3 LAN <--> Ethernet ports on the "main" AirPort to the WAN "O" port on the new AirPort Extreme.

Setup is about as simple as it gets. Here we assume....never a smart thing to do..... that the extending AirPort Extreme was either "new" as you mentioned or refurbished with default settings. If not, then you need to perform a Hard Reset on the AirPort Extreme that will be extending the network as follows:

Power up the AirPort Extreme if it is not already on and let it run a minute

Hold in the reset button on the back of the AirPort Extreme for 7-8 second and release

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

Power up the new AirPort Extreme and let it run for a minute. It is already powered on if you performed the Hard Reset mentioned just above.

Open AirPort Utility on your Mac Finder > Applications > Utilities > AirPort Utility

Click on the Other WiFi Devices button

Click directly on AirPort Extreme on the next window that appears

That will start up the AirPort Utility setup "wizard" automatically. 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 your AirPorts displayed.

Next to Base Station Name, type in a device name for the new AirPort. Keep the name short and simple, something like Extender for example, or you might use the name of room that the extender is located in.

Click Next

The next screen will indicate that the extending AirPort Extreme which you have just named will be configured to extend using Ethernet......so the correct settings will automatically be applied to the extending AirPort.

The wizard will set up everything for you automatically and correctly

When you see the message of Setup Complete, click Done and you are done. That's it.

You don't need to worry about what settings to use or things like Bridge Mode. Everything is handled for you correctly and automatically.

If you are really curious, you can open up AirPort Utility to take a look at the settings that were applied to the extending AirPort......but......do not change anything.

Apple discontinued the AirPort Extreme and other Apple routers in April 2018 and ceased selling the AirPort line of products at that time.

You might be able to locate a Refurbished or Used AirPort Extreme on a site like eBay.com or Amazon.com.

For best performance, you will need to connect another AirPort Extreme back to the "main" AirPort Extreme using a permanent, wired Ethernet cable connection because there is zero loss of speed with this type of setup.

While the "remote" AirPort Extreme can connect to the "main" AirPort tExtreme using a wireless connection, you will lose half or more of the potential speed on the network with this type of setup.

In other words, you will have a "bigger" network in terms of signal strength, but it will be a significantly slower network in terms of speed.

Even with the minis at 30' away I'm down to 450mbps wireless and 60' away below 200mbps.

If what you are calling a "mini" is actually an AirPort Express, 450 Mbp is the maximum theoretical speed of this device.

The "tower" model of the AirPort Extreme will do 1,300 Mpbs in theory.

I would locate any router up high in the room to allow for the best chance of line-of-sight from the router to the WiFi device. The center of the ceiling would be an ideal location, but may not be practical.

When I still had the older "flat" versions of the AirPort Extreme, I had 3 of them all connected via Ethernet and mounted on the ceiling in the 3 main areas of the house. Relatives wanted to visit just to use the wireless.

With two extremes in a 2700sqft home is there any reason to continue to use the express units?

Probably not, unless you plan to also connect them to an Ethernet "backbone" Even then, the Express only has 100 Mbps Ethernet ports, so that is the best that they could ever do.

If you are using the Expresses for AirPlay, you can change them from "extending" the WiFi network to "joining" the WiFi network. Then,,you won't have the huge speed loss.

Another thought.......Depending on how old your "main" AirPort Extreme is at this time, it might be time to take a look at a new "mesh" type WiFi network

I’m going to install another extreme and run cat5 to it. Do I run the cat5 from the output of my base to the input of the “new” one?

Connect an Ethernet cable from one of the 3 LAN <--> Ethernet ports on the "main" AirPort to the WAN "O" port on the new AirPort Extreme.

Setup is about as simple as it gets

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

Open AirPort Utility on your Mac Finder > Applications > Utilities > AirPort Utility

Click on the Other WiFi Devices button

Click directly on AirPort Extreme

That will start up the AirPort Utility setup "wizard" automatically

Next to Base Station Name, type in a device name for the new AirPort

Click Next

The wizard will set up everything for you automatically and correctly

The Hard Reset is not needed on a new AirPort, because the device is already in a factory default condition, so the initial setup screen will appear automatically.

It is important though, that the Ethernet connection is already established between the two AirPorts because the AirPort Utility setup "wizard" will see that connection and apply the correct settings to the extending AirPort for a wired connection.

If you do not first establish the Ethernet connection, then the setup wizard will not see a wired connection between the AirPorts and assume that you want to use wireless to connect the AirPorts. Once this setup is complete, if you then connect an Ethernet cable between the AirPorts, that will create a huge feedback loop and effectively crash the network on the extending AirPort.