Yes, you can use the Archer MR600 as a backup router if your primary router fails. Here are some important points to keep in mind:

- Mobile Internet: The Archer MR600 supports 4G+ Cat6 and can operate with a Nano SIM card, which allows you to use mobile internet without having to be at home.
- Wi-Fi router mode: You can also operate the Archer MR600 in Wi-Fi router mode by plugging an Ethernet cable into the LAN/WAN port if you do not have a 4G connection. However, this is not necessary if you want to use it as a backup for mobile Internet.
- SSID and password: You can configure the Archer MR600 to use the same SSID (network name) and password as your primary router. This can be set via the Tether app or the router's web interface.
- TP-Link OneMesh: If you already have a TP-Link OneMesh network, the Archer MR600 can also work with other OneMesh products to create a consistent and seamless network.

Through these functions, you can easily use the Archer MR600 as a backup router that uses the same name and password as your primary router without having to be at home.