How to set up Airport Express with Arris modem?

Have you turned off the router? Unplugged then plugged, rebooted?

Is it connected to the correct port on both ends of the ethernet cable?

Is your network set to configure automatically? (check on your computer)

Old network saying........Make just one change on a network.....and everything else will change.

What model number of Arris modem?

What model number of AirPort Express?

What operating system on your Mac or PC?

802.11n (2nd Generation)

Close enough. No model number needed.

The desktop is OSX.

Which version? Leopard, Snow Leopard, Mountain Lion, Mavericks, etc?

Still need the model number of the Arris modem when you can.

This is primarily a modem issue. The modem has associated with your desktop, so it "remembers" the desktop and it will not deliver a valid IP address to any other device to which it connects, like the AirPort Express.

So the trick is make the modem "forget" the desktop, so that it will associate correctly with a new device......your AirPort Express.

To do that, the modem must be completely reset back to its default settings. That means.....

1) Powering off the modem completely by pulling the power cable from the back of the device or from the wall AC jack.

2) Removing the backup battery from the modem

3) Disconnecting the Co-Ax cable and Ethernet cable

Instructions to remove the battery are here: ARRIS : Touchstone E-MTA TM822

Leave the modem powered off at least 30 minutes, longer is better.

Next, the AirPort Express must be reset back to factory default settings so that it will work with the new modem. To do that.....

1) Power off the AirPort Express and wait a minute or two

2) Hold in the reset button first, and keep holding it in for an additional 10-12 seconds while you simultaneously plug the power back into the Express

3) Release the reset button after the hold period, and allow a full minute for the Express to restart to the slow, blinking amber light

Now power off the Express again.

After you have waited at least 30 minutes with the modem powered off and the battery removed, reinstall the battery, connect the Co-ax cable, and connect the Ethernet cable from the modem to the WAN "O" port on the AirPort Express.

Power up the modem and let the modem run for 10 minutes by itself, then power up the AirPort Express and let it run for a few minutes

Now re-configure the Express using AirPort Utility on the Mac. To do that:

Open Macintosh HD > Applications > Utilities > AirPort Utility

Click on Other Wifi Devices

Click on AirPort Express

The utility will walk you through the setup. You can use the same wireless network name and password that you used before, or set up a new wireless network name and password.

both my desktop and laptop can't find it

Are you running the Mavericks (10.9.x) operating system on these Macs?

Do you happen to have an iPhone or iPad handy?

Bob's procedure should have worked. Can I suggest these connections?

Laptop <- Ethernet cable -> Airport Express (Lan Port)

Airport Express (WAN port) <- Ethernet cable -> TM822 RJ45.

The TM822 should allow release/renew of it's WAN address. Also curious if Ipv6 is being rolled out, which may be one potential issue.

Staying withIPv4, assuming the LAN DHCP server is the Express, you should be able to see and set up the express. If the TM822 is the LAN DHCP server, then the Express should be in Bridge mode.

procedure should have worked.

Assuming that the iPv6 settings on the Mavericks Macs are correct. (If the user is using Mavericks. We will know soon).

If the TM822 is the LAN DHCP server, then the Express should be in Bridge mode.

TM822 is a simple modem only (according the owner's manual that I downloaded)......not a modem/router or gateway.

Some Macs running Lion (10.7.x) and Mountain Lion (10.8.x) have also had problems with iPv6 settings.....not allowing the AirPort to appear in AirPort Utility. In double checking, I see that you mention that you were using (10.8.5). Is that still the case?

On the Mac laptop......

Open System Preferences (gear icon on the dock)

Open Network

Click on WiFi on the left to highlight it, then click Advanced at the lower right of the window

Click the TCP/IP tab

Make sure that the setting for Configure iPv6 is set to Link Local Only

Click OK

Click Apply

Close System Preferences

Now repeat the same sequence as above, except this time, click on Ethernet on the left side to highlight it, then proceed with the same steps.

Then do the same thing for both WiFi and Ethernet on the other Mac.

Once that is done, if you have connected the modem to any other device other than the AirPort Express, you must reset it again as I already detailed. A 30 minute power down should be sufficient.

This time, power up the Express and let it run a minute, then hold in the reset button for 10-12 seconds and release. Allow a full minute for the Express to restart to a slow blinking amber light, then power it off again.

Then power up the modem after the power down period and proceed as outlined above.

You did not mention whether you have an iPad or iPhone, but either of those devices can be used to set up the AirPort Express as well if you prefer.

You should try the setup with the iPhone or iPad if the Macs are still not cooperating.