There is a very long story behind this, but ultimately what I need to achieve is the following:
I have an 831 router sat on a LAN. It receives its eth1 (outside) address by DHCP. I also want to pick up a second DHCP address that can be used for hiding the "inside" hosts behind using NAT.
Is there any way I can get, for example, loopback1 to pick up an IP address from the outside LAN using DHCP?
I have no control over the LAN where this router is sat, so I can't reserve any addresses to use in a static config.