Trying to improve my wifi coverage, I have just bought a used Netgear
WN3500NP repeater. It just connects to my main router (OpenWRT) via
wifi and provides an additional access point further away. All is
working fine, but I notice one peculiarity...

I have my main router, the one which connects to my FTTC set up to do
the DHCP allocation of IP's, with everything allocated by the router
its own static IP, based on its MAC.

Now, everything which connects via the repeater, is given a virtual
MAC, with the first three sets of MAC numbers changed.

Problem is, items which connect via the repeater - things which once
had static IP's, now have to have a dynamic IP. I can add them via
'Static Leases' settings of my main router, but is there a better way?