Wireless backup but no possibilities to use the internetrouter for that (e.g. Hotel, student flat)

There is a somewhat unconventional setup that I used to use when I was traveling extensively and staying at hotels that only provide a Wi-Fi network........when I wanted to set up my own private wireless network in the room.

Configure an AirPort Express to "join" the WiFi signal. When it does this, the Ethernet port is "live". So, I would connect another AirPort Extreme to the AirPort Express using an Ethernet cable and set up the AirPort Extreme as a router to create a wireless network, establishing my own private WiFi network which had Internet access. The great thing about this was that I had my own private wireless network, so I did not have to "share" the hotel WiFi network with other guests, which could create some possible security issues.

I could connect a USB drive to the USB port on the AirPort Extreme and set it up for Time Machine backups. So, my laptop picked up the Wi-Fi signal from the AirPort Extreme and I could browse the Internet, check email etc while the laptop backed up automatically over the Wi-Fi to the USB drive at the AirPort Extreme.

Here's the rub. Other than an AirPort Extreme, there are very very few routers that will support a USB drive for Time Machine backups. Among them are the Synology router and upper end Asus routers. Most routers......even if they might have a USB port......will not support Time Machine backups.

The least expensive way to attempt the type of setup that I am mentioning is buy a used or refurbished AirPort Express and a used or refurbished AirPort Extreme. Another option would be to buy a Time Capsule, which is an AirPort Extreme with a built in hard drive that will support Time Machine backups.

I haven't used this type of setup in a number of years though, so while I see no reason why it would not work today, there are no guarantees that it work the way that you want.

I still have the old A1264 AirPort Express that I used to use on the road to join hotel Wi-Fi networks, so I set it up to "join" my regular Wi-Fi network here at the house. When I connect my laptop to the Ethernet port on the Express and turn off the WiFi on the laptop, my laptop connects to the Internet just fine. Your AirPort Express needs to do the same.

So, you need to try some restarts, power downs, maybe another Ethernet cable etc to get things working with a good Internet connection on the Express. It is critically important to have the AirPort Express deliver an Internet connection at its Ethernet port in the setup that I described above, because the Express will be connecting to a second WiFi router that will provide a private network with Internet access, so the Mac on the network there will be able to work normally using the WiFi signal that the second router is providing.

If that second router is an AirPort Extreme and you connect a USB drive to the USB port on the AirPort, you will be able to back up the Mac using Time Machine to the USB drive while the Mac simultaneously remains connected to the Internet. In other words, Time Machine backups will occur over Wi-Fi seamlessly while the Mac remains normally connected to the network for browsing, etc.

Check this article about your options:

Backup disks you can use with Time Machine - Apple Support

My Mac is backing up to my TimeCapsule wirelessly.

First things first. Power off the second AirPort for now......which you call the Extreme......and work only with the AirPort Express which is joining the WiFi network.

Make sure that you can turn off the WiFi on your Mac and connect it directly to the AirPort Express using the Ethernet cable and get a good Internet connection that way. You may need to power off, restart etc the AirPort Express or even reconfigure it again.

When you have a good Internet connection at the AirPort Express, then we can go to the next step.

Once you have the Express working correctly, please do the following on your Mac that is connected to the Express:

Open System Preferences, then open Network

Click on Ethernet on the left panel

Click on the Advanced tab at the lower right of the next window

Click on the TCP/IP tab at the top of the next window

What is the IPv4 Address that is assigned to your Mac?

You don't have to put down the entire address. For example, if it is something like 192.168.1.10, just respond with 192.168.x.x. Or, if you are using an Apple router as your "main" router, the IP address will likely look something like 10.0.1.15. In that case, just put down 10.0.x.x

Now I'm looking forward for testing it in a public network (hotel.. eg,)

As long as you set up the AirPort Express to "join" the WiFi network and enter the password to connect, you will not have any problems.

If you plan to test this setup out at a hotel, keep in mind that some hotels limit the amount of connection time on their WiFi networks.......... 1 or 2 hours for example......in which case you will need power off the AirPort Express and then power it up again and connect to the hotel WiFi network again.

If the Express will be joining a WiFi network that provides a constant signal with no time limits on the connection, that will make things a lot easier.

Something that I'm not fully understanding in your post is to what device will you be backing up your notebook to? What I am getting from your post is that it would be to an external drive that you would want to connect to a router so that you can perform those backups wirelessly. Am I misunderstanding that?

Assuming you already have a wireless router that accepts an external drive (connected by USB), your goal is to use this router/drive combo for your backups while still having your notebook gain Internet access through another router (that you have no access to.)

You mention that you have this working at your home. I believe the key their is that you have administrator-access to both of your routers. You will rarely have this same situation away from home. Just not sure why just connecting the drive directly to your notebook would not be a far simpler solution overall.

Going back to the Time Capsule. Unlike the AirPort Express, where you can have it "join" an existing Wi-Fi network, the TC cannot. At least, not for the purpose of sharing its drive. Unfortunately, the Express does not support external drives, just printers for this purpose.

No worries. "Old" means different things to different people, so I was trying to clarify an earlier statement that the AirPort Express could join a wireless network and provide an Ethernet signal. Only the two most recent versions of the Express have this capability.