Modern smartphones like the Xiaomi Redmi 9 allow two SIM cards at once, which is incredibly convenient for separating work and personal contacts. However, there is often a situation when a user wants to use mobile Internet from a second operator whose tariff offers better conditions or better coverage in a particular area. By default, the Android system may not always automatically choose the desired data slot, requiring manual one.
The process of changing the source of the Internet connection in the MIUI shell installed on the Redmi 9 is quite logical, but it has its own nuances. You do not need to physically rearrange the cards or reboot the device every time. The switch is programmatically through the settings menu, where you can assign a priority slot for data transfer. It is important to understand that activating the mobile Internet on the second SIM card will automatically turn it off on the first one, since the communication module only works with one data stream at a time.
In this guide, we will take a detailed look at all the steps needed to set up correctly, and we will look not only at the basic algorithm of actions, but also at possible problems with access points. APN, And we'll also focus on traffic savings and networking. 4G/LTE, Make your connection stable and fast.
Basic setting of data priority in MIUI
The first step to solving the problem of how to switch the Internet from one SIM to another on Xiaomi Redmi 9 is to refer to the main menu of network settings. MIUI It groups all the SIM card settings in one place, which makes it easier to manage. You need to open the Settings app and find the partition. SIM-Maps and mobile networks. This is where you have the control center for all the communication functions of your device.
In the menu that opens, you will see a list of installed SIM cards, usually designated as SIM 1 and SIM 2. Below is the Internet (or "Mobile Data") field, which indicates which of the cards is currently active to access the network. Clicking on this item, the system will prompt you to select your preferred SIM card. After selecting the marker will move to the desired slot, and the network indicator at the top of the screen (E, 3G, 4G, LTE) should be activated for the selected operator.
It's worth noting that this is changed instantly, without the need to reboot. However, if the Internet icon does not appear immediately, try to turn on and off flight mode. This will force the device to re-register the network with new parameters. Also make sure that the SIM card you choose is actually activated mobile Internet service from your carrier.
⚠️ Note: When you switch the internet to a second SIM card, background applications using the network may temporarily lose connection. Make sure you have important data that is transmitted in real time to avoid losing it.
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For a quick change of SIM card for the Internet, you do not need to go to the settings every time. Add the SIM Switch widget to the desktop or to the notification curtain through the Quick Settings editing menu.
Configure APN access points for the second operator
Often you switch priority to a second SIM card, but the Internet didn't work. 90% of the time, the problem is that the APN (Access Point Name) settings are not available or incorrect. When you first insert a new SIM, the Xiaomi Redmi 9 usually automatically downloads the correct settings from the database. However, when you manually switch between long-established cards, this process may not start automatically.
For check and manual settings go to the Settings menu → SIM-Select the SIM card to which you switched the Internet (for example, SIM Find the access point (APN). If the list is empty or the selected point is not working, click the New Access Point button (usually in the bottom menu or through three dots in the corner).
It is important to enter the exact data provided by your carrier. An error in even one character in the name or password field will cause the Internet to fail. Usually, just enter the point name (APN), the remaining fields can often be left empty or by default. After entering, be sure to click Save and activate the created point by placing a marker next to it.
Typical APN settings for popular operators
After saving the settings, it is recommended to turn on the flight mode for a few seconds so that the communication module applies new parameters. If after this manipulation the Internet does not appear, check whether the traffic limit on this SIM card is exhausted, as this also blocks the connection.
Network management and communication standards
The quality and speed of the Internet connection on Xiaomi Redmi 9 directly depend on the type of network chosen. In today’s environment, the best choice is the 4G standard (LTE), which provides high data transfer speeds. However, in some regions, 4G coverage can be unstable, and the phone will constantly switch between 3G and 4G, consuming battery power and causing connection breaks.
The SIM card settings menu (the one chosen for the Internet) has Network Type or Network Preferred. Here you can choose Preferably 4G. If you are in a low reception zone, it makes sense to temporarily limit the network to 3G for stability, although the speed will be lower. There is also the option of choosing 4G only, but this mode should be used with caution: if it is enabled, you may lose the ability to receive normal voice calls if the operator does not support VoLTE technology.
- 📶 Preferably. 4G — Optimal mode for most users, providing a balance of speed and stability.
- 📶 Only 4G — mode for areas with excellent coverage, but with the risk of loss of voice communication without VoLTE.
- 📶 3G/2G — used as a backup option in places with poor signal or to save charge.
If you use a second SIM card primarily for the internet, make sure that the settings of that particular SIM card allow roaming data transfer if you are outside your home region. Sometimes operators block 4G in the absence of this tick, even within the country, if you are.
Table of comparison of SIM slots characteristics on Redmi 9
Many users wonder if there is a difference between the first and second SIM card slots on the Xiaomi Redmi 9.Technically, both slots support modern communication standards, but there are nuances in their collaboration, especially when using microSD cards, since the second slot is often a combined slot.
Below is a table showing the main differences and possibilities of slots, which will help you plan the installation of cards correctly for maximum ease of use of the Internet.
| Characteristics | SIM 1 slot | SIM 2 slot (Hybrid) |
|---|---|---|
| Support for Nano-SIM | Yes. | Yes. |
| Support for 4G/LTE | Yes (main) | Yes (with active SIM 1) |
| Simultaneous operation of 4G+4G | No (only one active) | No (only one active) |
| Compatibility with microSD | No. | Yes (instead of SIM 2) |
You can see from the table that you can use any slot for the Internet, but if you also need a memory card, then for the second SIM card (which is often used as an additional one for the Internet), you will have to sacrifice either a memory card or a second SIM.
When switching between slots, make sure that the hybrid slot has a SIM card installed, not a microSD, if you plan to use it for data transfer. Physical card replacement requires turning off the phone or using a tray, which is less convenient than software switching.
Saving traffic and controlling background activity
When you switch the Internet to a second SIM card, you have to consider that all applications will start consuming traffic from that SIM card. If that number has a tariffed or limited packet, uncontrolled background consumption can quickly run out of resources. MIUI offers tools for control, but they need to be configured correctly.
In Settings → Connection and Sharing (or in the Security → Data Application), you can set the restrictions for each application separately. You can prevent certain programs from using the mobile network by allowing them to access only via Wi-Fi. This is especially true for heavy applications such as YouTube, Instagram or cloud storage.
You should also set a traffic limit. In your mobile network settings, you can set a monthly plan, the system will alert you when you are approaching the limit, and can automatically turn off mobile Internet when you exceed it, preventing unexpected expenses.
⚠️ Attention: Social media apps and instant messengers often update content in the background. After switching to a new SIM card, check your background activity settings to avoid hidden megabyte consumption.
☑️ Traffic control
Solutions to Connection Problems
Even with the right setup, there can be situations where the Internet doesn't work after a switch. IP-In such cases, resetting your network settings helps, not to delete your personal files or contacts, but to return all network settings to factory values by removing stored Wi-Fi passwords and Bluetooth settings.
To perform the reset, go to Settings → Connection and Sharing → Reset Wi-Fi, mobile networks and Bluetooth. Once confirmed, the phone will reboot the network modules. This often solves problems when the phone "sees" the network but does not transmit data.
Another reason could be a lock on the part of the operator, so make sure that the second SIM card is not worth it. PIN-A code that requires input every time you turn on, or that the card is not blocked due to debt, also check if your SIM card supports the technology. 4G — Old cards issued many years ago can only work in the 2G/3G, What makes the use of the modern Internet extremely slow.
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If after all the settings the Internet does not work, reset the network settings or check SIM-card in another device to eliminate hardware malfunction.