There is a sollution
(from memory, so the actual button names may be slightly different)
You need to findt the listed 'eth's in the web admin, either under network setup or under device settings for the core.
Then change one of the 'eth's to say DHCP instead of the IP it currently has, that sets it up to receive a DHCP IP from the router.
You may have to apply changes/save a couple of times, and possibly also reboot, but it should work.