Background: I recently upgraded my Dell R740xd to use a Broadcom BCM57810 10GbE fiber card as my primary network interface and physically removed the onboard NIC (which was eth0). After the change, all WebUI buttons in the Docker dropdown stopped working.

Symptoms:

• Clicking the WebUI button on any container did nothing

• Using browser Developer Console revealed the error: Unable to open a window with invalid URL 'http://[ip]:[port:XXXX]/'

• The [ip] and [port:XXXX] template variables were never resolved

• All other dropdown functions (Start, Stop, Restart, Console, Logs) worked fine

• The issue affected ALL containers, not just specific ones

Root cause: After investigating, I found that Unraid's Docker manager appears to resolve the [ip] template variable by looking for eth0 as the primary interface. Since the physical NIC was removed, eth0 no longer existed, and the template variable could not be resolved.

Evidence: /var/local/emhttp/network.ini showed the correct IP under [eth3] but there was no [eth0] section. The network.cfg on /boot also had no eth0 entry after I updated it to use br3/eth3 as the primary interface.

Workaround: Creating a dummy eth0 interface with the correct IP at boot resolves the issue:

ip link add eth0 type dummy
ip link set eth0 up
ip addr add YOUR.SERVER.IP/24 dev eth0

I added this to /boot/config/go to make it persistent across reboots:

# Create dummy eth0 for Unraid WebUI compatibility (physical NIC removed)
ip link add eth0 type dummy 2>/dev/null
ip link set eth0 up
ip addr add YOUR.SERVER.IP/24 dev eth0 2>/dev/null

Questions:

1. Is this a known limitation? Should Unraid support using a non-eth0 interface as primary?

2. Is there a cleaner solution, such as a setting to specify which interface to use for the [ip] template variable?

3. Could network.cfg be updated to support a PRIMARY_INTERFACE setting?

Environment:

• Unraid version: 7.3.0

• Hardware: Dell R740xd

• Primary NIC: Broadcom BCM57810 10GbE (eth3/br3)

• Onboard 4 port NIC: Physically removed

You must set the new NIOC as eth0, that can be done in Settings - Network Settings - Interface Rules (reboot required).

7 hours ago, JorgeB said:

You must set the new NIOC as eth0, that can be done in Settings - Network Settings - Interface Rules (reboot required).

I hope you are trolling since that is just not possible.

Update/Workaround

The Interface Rules page only allows swapping MAC addresses between existing interface names (eth2↔eth3), it does not allow renaming an interface to eth0.

The working workaround is to create a dummy eth0 interface at boot by adding the following to /boot/config/go:

bash

# Create dummy eth0 for Unraid WebUI compatibility (physical NIC removed)ip link add eth0 type dummy 2>/dev/null
ip link set eth0 up
ip addr add YOUR.SERVER.IP/24 dev eth0 2>/dev/null

This resolves the [ip] template variable in Docker WebUI URLs without requiring the physical onboard NIC to be present.

Suggestion for Unraid developers: The WebUI URL template resolution should not be hardcoded to eth0 but should instead use the primary/active interface IP.

Edited May 30May 30 by Christian_P

16 hours ago, Christian_P said:

I hope you are trolling since that is just not possible.

Not sure what you mean, as mentioned, you can set whichever NIC you want as eth0

4 minutes ago, JorgeB said:

Not sure what you mean, as mentioned, you can set whichever NIC you want as eth0

Not on my server

Delete /config/network-rules.cfg on the flash drive and reboot

9 minutes ago, JorgeB said:

Delete /config/network-rules.cfg on the flash drive and reboot

I will try that

8 hours ago, Christian_P said:

I will try that

8 hours ago, JorgeB said:

Delete /config/network-rules.cfg on the flash drive and reboot

That solution worked!

Thank you !!