new interface doesn't work

Hi all,

I have a problem with a newly "installed" interface on my Astaro Firewall.

I have a fully virtualized system with KVM. One virtual machine is the Astaro Firewall (8.302) with 5 virtual NICs (RTL8139). This worked fine since installation and all NICs are fully functional.
Today I tried to attach a new virtual NIC to Astaro without any success.
I guess that on KVM all was properly done, because I can see 6 NICs with "lspci" on CLI of ASG. But with ifconfig I can only find 5 NICs: eth3 was changed to the new one (new MAC) - the old eth3 was changed to eth3_tmp (with this name I can also bring it up with ifconfig - the problem is, that I cannot see or configure it on the Web Interface for further use.

Is there any way to manually lock interface naming and give the new interface eth5?
I don't want to newly install Astaro and restore from Backup - there must be a was without reinstallation.

Thanks,
Philipp