New Xfinity (1Ghz) Modem and Apple Airport Extreme Gen 6

1 Is it worth just enabling the 2.4 and forgetting the 5ghz? Even though it's wicked fast, it seems unstable.

Since the AirPort base stations are simultaneous dual-band devices, you will not be able to disable a single radio. Either you disable both or none ... so this wouldn't work. What you can do is use different network names for each band and "steer" your devices to the appropriate band. For example, for devices in the same room as the base station, connect them to the 5 GHz band for the best overall wireless performance. Those that will roam, should be connected to the 2.4 GHz band.

2 Are there any known issues with Comcast 1gb Modem? Can the fact that I am only buying up to 400mbps be an issue? Could comcast be choking this?

Of course anything is possible, but you should be getting near the 400 Mbps Internet speeds at the modem. A simple test would be to connect a computer directly to the modem by Ethernet and take a speed measurement to verify you are getting what you are paying for. We can assist you with troubleshooting your wireless/wired network after that.

3 I have a few TV's and I wanted to put them on the 5Ghz due to speed, but their wifi antenna's only show a small amount of signal. When I switch to 2.4 the TV's get a robust signal, although slower. (70mbps vs 300mbps +/-)

For media devices, the best choice is really to go with wired connections over wireless ... but if wireless is desired, then the 5 GHz band would be preferable ... but only if the device is in the same room as the base station. The higher frequencies used by the 5 GHz band has a more difficult time traveling through objects, like walls.

4 My ethernet cable to one of the extender networks routers no longer works with the new gen 6 airport. Weird.

We would need to know a bit more about your current network configuration to be able to help you troubleshoot this. For example, are the two extending base stations, connected by Ethernet, connected directly back to the "main" base station or do you employ any Ethernet switches between them? What is the cable run lengths between each of the extenders and the "main" base station?

Ok, the xFi Advanced Gateway is not a simple modem, but a combination modem and wireless router. As such it is providing the routing functions for you overall network. In this case your AirPort base stations need to be reconfigured as bridges. That is, their routing functions (DHCP & NAT) should be disabled.

If I understand your network configuration properly, then:

• You have an AirPort Extreme directly connected to the xFI gateway by Ethernet. Both are in the same closet.
• Both the XFi and this Extreme are broadcasting a wireless network ... correct?
• Is this Extreme reconfigured as a bridge? That is, is its Router Mode = Off (Bridge Mode)?
• From the closet you have two Ethernet cable runs that go upstairs from this location, but one of them is not working properly ... or at all ... correct?
• For the one that works, you have connected another Extreme and it too is broadcasting a wireless network ... correct?
• For the one that doesn't you have another Extreme connected wirelessly to the "main" Extreme to extend its wireless network ... correct? ... and then another one to attempt to extend that one ... correct?
• For the Ethernet run that is not working, what is the estimated run length? Per chance is it over 328'?

Based on your responses, I will try to assist you with getting this sorted out.

We should be able to do it via this platform.

My basic strategy is to start simple, and then, work in each of the networking components one-at-a-time after each success.

This would take us back to where you only have the gateway and the "main" Extreme running. We would verify Internet connectivity via both wired and wireless connections to that Extreme ... before we move on.

If you're game, then I suggest that you power-off all of your extending base stations, and then, go ahead and verify that Internet connectivity of the "main" base station. Once you're satisfied everything is working to your needs, post back your results so that we can start with the first extender.

Having a Mac notebook, with an Ethernet port will come in handy when we do proceed.

Assuming that you were successful with this first part of the setup, here's the next part to get each of the extending base stations ready:

Some upfront assumptions/activities:

• To facilitate the setup, you may find it easier to have both the "main" and "extending" base stations in the same location. After a successful setup, you can then move the extending base station to the desired location.
• Both the "main" Internet router and the "extending" routers are AirPort base stations.
• The Ethernet cable, coming from the "main" base station, going to the to the WAN (circle-of-dots) port on the extending base station is initially disconnected.
• You have verified that the Ethernet port (or cable) that will connect to the extending base station is operating at 1000baseT/full-duplex mode. (Note: This is where having an Ethernet-equipped notebook will come in handy.)
  • To verify this:
    • Temporarily connect the notebook to the Ethernet wall outlet using an Ethernet drop cable.
    • Go to System Preferences > Network > Ethernet > Advanced > Hardware tab
    • Note the values for Speed and Duplex. They should be 1000baseT & full-duplex, respectively.
• The extending base station is NOT connected to power.
• Verify that the Mac, hosting the AirPort Utility, is configured (as a minimum) for "IPv6-Link local only" mode.
  • To do so: System Preferences > Network > Wi-Fi > Advanced > TCP/IP tab > Configure IPv6: Link-local only. I also recommend doing the same for the Ethernet connection on your Mac. (Note: The AirPort Utility relies on IPv6 to locate an AirPort base station on the network.)
• Perform a "factory default" reset on the extending base station.
  • Using a paperclip, or something similar, gently hold in the reset button on the base station.
  • While still holding down the button, plug the base station into a power source. Wait until the base station's status LED starts flashing rapidly, then release the button.
  • Allow a full minute for the base station to restart to a slow, blinking amber LED light status. (Note: This just means that there are some additional setup steps that may be required.)
• Leave the extending base station connected to power. Alternately, remove it from power if you will want to finish the roaming network setup at a later time.
• Repeat these steps for each extending base station that you plan on using in your overall network configuration.

Ethernet runs are limited to 100 m (or 328 ft.) If the run from the "main" Extreme to the upstairs family room is less than that, you should be good. Also, you check to see by connecting your notebook to that port upstairs and it still shows a 1000baseT connection. However, the only true way to validate it would be to perform a throughput test over this run. For that I would use something like TamoSoft's Throughput Test ... which may be getting things a bit more complicated.

Most likely the reason the AirPort Utility is having trouble finding it may be due to either the IPv6 or Bonjour protocols not making it to this location. Again, the AirPort Utility uses these protocols to locate a base station. One thing you can do, is bring this particular base station to the same room as the "main" and temporarily connect it via a short Ethernet cable, and then, set it up there. Once successfully configured, you can bring it back to the desired location.

Ok, so the Utility is showing that both the "Family Room AirPort" and "Jill's AirPort" are connected back to the "Main AirPort Extreme" by Ethernet and the "Lower Family AirPort" is connected back to the main by wireless. Is this correct and what you want? Remember, if the main is in a closet, that lower AirPort is going to have a difficult time getting a strong signal from it to extend it with any useful bandwidth.

If you click on the yellow triangle, what error(s) does it tell you that this base station is having? ... or is it telling you that it is no longer available and you have the option to "forget it?"

Some things that may help:

• Use AirPort base station names that are 16-alphanumeric characters or less. Don't use special characters or spaces in the name.
• Assign each "extending" base station a static local IP address instead of them using DHCP to get an address from the main base station.
• Be sure to enable, as a minimum, IPv6 Link-local only on each base station. The AirPort Utility uses IPv6 to discover base stations.
• When extending, using a wireless connection, like you are doing with "Lower Family AirPort," that base station's placement is critical. I wrote the following user tip article on this exact subject: AirPort - Optimal Base Station Placement - Apple Community

If you need help with any of these items or would be willing to "start from scratch," I'm game to assist you with doing so.

Since I will need to drop-off for the rest of today, I wanted to leave you with the last part of setting up your roaming network.

As such, for the two base stations that will connect back to the main base station by Ethernet, give the following a try:

1. Connect the Ethernet cable to the extending base station.
2. On your Mac, click the Wi-Fi icon on the macOS menu bar. The extending base station should now show up under the title: New AirPort Base Station in the Wi-Fi's dropdown menu.
3. Click on the extending base station and the AirPort Utility should now start up.
4. Enter a base station name for the extending base station, and then, click on Next. Again, I suggest using a name that uses 16 alphanumeric characters or less that does not include either spaces or special characters.
5. The next screen should have the title: Setting up this AirPort <Express/Extreme/Time Capsule> to extend "<the main base station name>" using Ethernet. This is telling you that the AirPort Utility has determined that you will be extending using an Ethernet connection between the two base stations. This is what you want for a roaming type network.
6. When you get the "Setup Complete" message, click on Done.

Ok, thanks for images. It appears everything is fine with the Ethernet connection. If these are the values you see at both Ethernet runs were the extending base stations will be connected to, you're all good to go with the next part which is to set up each extending base station. Also, it appears that Comcast is providing you with IPv6 service, so you don't need to worry about checking for that IPv6 Link-local only mode setting. In this case we would want to leave the Configure IPv6 option to Automatically ... .as it already is.

If you have already reset the base stations, you should now be at this part where the extending base stations are NOT connected to Ethernet, but are connected to power.

Starting with either base station, we want to go through those last steps that I provided you earlier before I had to drop off.

For convenience, I listed them below ...

1. Connect the Ethernet cable to the extending base station.
2. On your Mac, click the Wi-Fi icon on the macOS menu bar. The extending base station should now show up under the title: New AirPort Base Station in the Wi-Fi's dropdown menu.
3. Click on the extending base station and the AirPort Utility should now start up.
4. Enter a base station name for the extending base station, and then, click on Next. Again, I suggest using a name that uses 16 alphanumeric characters or less that does not include either spaces or special characters.
5. The next screen should have the title: Setting up this AirPort <Express/Extreme/Time Capsule> to extend "<the main base station name>" using Ethernet. This is telling you that the AirPort Utility has determined that you will be extending using an Ethernet connection between the two base stations. This is what you want for a roaming type network.
6. When you get the "Setup Complete" message, click on Done.
7. Repeat the above steps for the second extending base station.
8. We will figure out what to do with the third base station after you confirm that you can gain Internet access at both of these extending base stations.

What is the make & model of the Comcast-provided modem? Since the "main" Extreme is in a closet, we may want to reconsider even having its wireless radios enabled as the signal (especially the 5 GHz one) will have trouble going very far with any useable bandwidth.

Is this location wired for Ethernet or are you just running Ethernet cable runs as needed? Does the closet where the modem and "main" Extreme also where the Internet comes into the house?

Just so you know, the AirPorts can't be used in a "daisy-chain" like fashion to extend a wireless network. Instead, they work in sort of a wheel-like fashion, with the base station to be extended at the hub, and the extending base stations on any of the spokes ... and why you see the "Family Room AirPort" and "Stairway AirPort Extreme" connected wirelessly (dotted line) back to "Jill's AIrPort."

Btw, does your forum username stand for Fender Telecaster, per chance?