# Modem Connection
## Physical Connections
Use the included tool hex wrench to lose all of the four pieces of hexagon bolts on the front side of the 4G router, then open the case. You can find the Mobile Modem in the top left corner of the image below.
The Quectel mobile modem has three IPEX connectors, including. `Main`, `GNSS`, and `DIV`. The `Main` connector goes to the **main mobile antenna** on the top left side, and the `DIV` connector goes to the **alternative mobile antenna** on the top right. Both use thinner jumper cables compared with the Wi-Fi antenna cables.
To ensure the portable modem is installed correctly, check the below subjects:
* Check if the above `Main & Div` sockets connect to the correct mobile antennas.
* Check if the attached jumper cables connect tightly.
* Check if the two pieces screws nearby the jumper cable are installed correctly.
* Touch the top cover on the mobile modem and test if the temperature is too hot.
*\*`GNSS` The socket is for connecting to a GPS antenna.* \
*\*On **Sierra Wireless** modems, the alternative mobile socket is `AUX`, and the GPS antenna socket is `GPS`.*
{% hint style="info" %}
To avoid distorting or breaking the IPEX connectors on the mobile modem, do not reconnect the jumper cables unless the router is malfunctioning.
{% endhint %}
Physical Connection on the Mobile Modem
## Virtual Interfaces
When the mobile modem is correctly installed and the router is powered on, go to the [command-line ](/ezr33/advanced/command-line.md)interface to check the virtual interfaces created by the mobile modem. The [`Mobile interface`](/ezr33/configuration/mobile-modem.md#mobile-status) uses one of the virtual interfaces to set up the internet connection.
After accessing the `command-line` interface, use the command **`ls /dev`** to check all the virtual interfaces on the EZR33 router. Check the return value and find if the router has two interfaces below. If unable to locate these interfaces, recheck the above 6.2.1 physical connections.
* `cdc-wdm0`: Use by the [`QMI-cellular`](/ezr33/configuration/mobile-modem.md#qmi-cellular-protocol) protocol
* `ttyUSB2`: Use by the [`4G-PPP`](/ezr33/configuration/mobile-modem.md#4g-ppp-protocol) protocol
```
root@OutdoorRouter:~# ls /dev
bus memory_bandwidth mtd4ro mtdblock5 random ttyS15 ttyUSB1
cdc-wdm0 mtd0 mtd5 mtdblock6 shm ttyS2 ttyUSB2
console mtd0ro mtd5ro net tty ttyS3 ttyUSB3
cpu_dma_latency mtd1 mtd6 network_latency ttyS0 ttyS4 urandom
full mtd1ro mtd6ro network_throughput ttyS1 ttyS5 watchdog
gpiochip0 mtd2 mtdblock0 null ttyS10 ttyS6 zero
gpiochip1 mtd2ro mtdblock1 port ttyS11 ttyS7
hwrng mtd3 mtdblock2 ppp ttyS12 ttyS8
kmsg mtd3ro mtdblock3 ptmx ttyS13 ttyS9
log mtd4 mtdblock4 pts ttyS14
```
---
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