> For the complete documentation index, see [llms.txt](https://docs.mikopbx.com/mikopbx/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mikopbx.com/mikopbx/english/faq/management/backup-internet.md).
# Backup Internet and Provider Re-Registration
Configuring Backup Internet
If your PBX is behind NAT and its public IP address changes, the PBX may not receive incoming calls until it re-registers with the provider, which by default can take 2–6 minutes.
## Create the IP Check Script
1. Connect using SSH into your MikoPBX (documentation about different ways to do that - [here](/mikopbx/english/faq/troubleshooting/connecting-to-a-pbx-using-ssh.md))
2. Create a new script file with this command:
```bash
cat > /storage/usbdisk1/mikopbx/custom_modules/update_ip.sh
```
The system will wait for input; paste the following script into the terminal:
```bash
#!/bin/bash
# File to store the previous IP
IP_FILE="/tmp/last_ip.txt"
# Command to retrieve the current public IP
CURRENT_IP=$(/usr/bin/curl -s https://checkip.amazonaws.com)
# Check if the file with the previous IP exists
if [ -f "$IP_FILE" ]; then
LAST_IP=$(cat "$IP_FILE")
else
LAST_IP=""
fi
# Compare the current IP with the previous IP
if [ "$CURRENT_IP" != "$LAST_IP" ]; then
/bin/busybox logger -t 'UpdateIP' "IP changed: $LAST_IP -> $CURRENT_IP"
echo "$CURRENT_IP" > "$IP_FILE"
# Trigger an Asterisk command
/usr/sbin/asterisk -rx 'pjsip send register *all'
fi
```
3. Press **CTRL+D** to finish.
4. Make the file executable:
```bash
chmod +x /storage/usbdisk1/mikopbx/custom_modules/update_ip.sh
```
## Schedule the Script
1. Go to the MikoPBX web interface → "**System"** → "**System file customization":**
"System file customization" section
2. Open the file: **`/var/spool/cron/crontabs/root`**
"crontabs/root" file
3. Append the following line to the end of the file:
```
*/1 * * * * /storage/usbdisk1/mikopbx/custom_modules/update_ip.sh > /dev/null 2> /dev/null
```
This schedule runs the script every minute to check for a changed public IP. If the IP has changed, it re-registers all providers.
Editing file crontabs/root
{% hint style="success" %}
If the IP changes, you’ll see an informational log in `system/messages` stating the old and new IP addresses.
{% endhint %}
---
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