Hi there i am trying to set up an server using this guide Ubuntu home net server config

i get the error "Failed to save interface : An existing Ethernet interface must be selected for this bridge to use" at this part of the guide.

I will use 192.168.0.1/24 for the purposes of this guide. This is the standard ip range to use for local home networks. Go to the "Interfaces Activated at Boot Time" tab and click eth_SAFE to configure it if it is there already. If it isn't there already (it probably isn't) then click "Add a new interface". Enter the following details:
"Name" - eth1
"IP Address" - Make sure the "Static" radio button is checked, and enter 192.168.0.1 into the text box.
"Netmask" - Should be 255.255.255.0
"Broadcast" - 192.168.0.255
"Activate at boot?" - Set to yes

Any suggestions on how to fix it?