Does anyone know how to get rcp to work with dhcp?

I can't see how to get an 'equivalency' set up, as the hosts.equiv file works from the name of the host/user and not from a sub set of the IP address.
For example I have a client laptop running with DHCP that is assigned address 10.90.1.1 and I want to copy files from/to a server on 10.90.1.10.

I can manually rlogin/rsh to 10.90.1.10 and I can also use:

rcp /tmp/file 10.90.1.1:/tmp/file

from the server, but I can't see how to copy from the client, as it's name is not in the hosts file as it gets a different ip address each time from dhcp.

Am I being stupid? (don't answer that bit......)