Brief description of the service and overview of purpose of Q&A
...
A smartphone is the recommended device since the since the Duo Mobile app provides the greatest level of security and flexibility. The app generates passcodes for login (even without cellular connectivity) and can receive push notifications for easy, one-tap authentication. Duo Security offers multiple other ways to authenticate with Duo. Besides a smartphone, you can use an older cell phone, landline (such as your office or home phone), a tablet, printable backup codes or a security key.
What devices are supported by Duo Mobile?
...
How do I set up an older cell phone, or use a smartphone without the Duo app installed?
(This option will no longer be available for new enrollments Dec. 1 and will be unavailable for all accounts beginning March 4, 2024)
Duo will work with any cell phone that can receive text (SMS) messages. When adding a device in this mode, first choose "Mobile Phone," and on the next screen enter the phone number. After confirming the phone number, set the phone type as "Other (and cell phones)" and the mobile device will be added.
...
What do I do if I don’t have my mobile phone with me?
- Duo can call your office line if you have set it up as an alternate number. We recommend adding at least your office line, and possibly other lines as appropriate. For example, you may want to have a spouse's mobile number as an option in case of emergency.
- It is highly recommended that you generate and print backup codes that you can use when you do not have access to your other devices, such as phone. Connect to https://accounts.lehigh.edu/duocodes/generate to generate and print these codes. Remember to store the codes in a safe location such as your wallet.
- You can use a USB Security Key, available from YubiKey and other vendors. Again, this must be set up in advance. We have tested the following options.
I will be getting a new phone soon. How can I make a smooth transition to a new phone?
Before wiping your old phone, you should print out a new set of one-time-use codes to help with enrolling your new phone. Once you have the print-out, download the Duo Mobile app on your new phone. Then open a web browser and go to the Duo Device Management page.
On the Device Management page, press the green "Enter a Passcode" button, and enter one of the codes you printed out. 
...
Ideally, you will have other options for authenticating. Did you set up an alternate cell, landlinethe app on another cell phone, tablet, set up a security key, or print out backup codes at go.lehigh.edu/duobackup ? If not call or email the Help Desk for assistance removing the device from your account.
...
I use a landline for Two-Factor Authentication (2FA), and I’m going away for a week. Can I still use the service?
(This option will no longer be available for new enrollments Dec. 1 and will be unavailable for all accounts beginning March 4, 2024)
Yes, you can forward your enrolled phone to another number (or add the other number temporarily at the 2FA self-service portal).
...
Yes, Duo will work from pretty much anywhere you can access the Internet. We recommend that you have the Duo mobile app installed on your phone while traveling. If you’re planning to travel without your phone , please contact us in advance for please print out backup codes or set up a security key. Please contact us if you need assistance.
I'm an international student/employee; how will Duo work for me?
The Duo app will work internationally as long as you have cellular data, and is recommended as a primary authentication method. If you prefer phone call verification, make sure to add the appropriate country code when applicable. Generating backup codes or set up a security key to have handy when your connection may not be available is also recommended. Duo might be unavailable is countries sanctioned by the United States due to export control regulations. Contact the Help Desk for assistance in changing your phone number, installing the app, or obtaining a one-time use backup code.
I will be using the Internet only at wifi hotspots and won’t have cell phone access while traveling, will Duo still work?
(The Duo mobile generated passcodes, SMS, phone callback option will no longer be available for new enrollments Dec. 1 and will be unavailable for all accounts beginning March 4, 2024)
Yes, Duo Mobile application can be used to generate passcodes on airplanes or in remote regions where Duo Push, SMS-delivered passcodes, phone callback or cellular service may be unavailable or difficult to use. Duo Push can use a Wi-Fi connection to function. If you can access the Internet from your mobile device, you can receive push notifications.
I’m an employee who will be retiring soon. Will I be required to use 2FA after I retire?
When you leave Lehigh your staff affiliation will change to retiree, and as such, you will no longer be required Yes, to meet current security requirements, beginning around January 1st, 2024 retirees will need to be enrolled in 2FA.Duo to use their Lehigh accounts.
Requested a push notification but did not receive one on iPhone?
...