EP.NET ???

begin kludge

  interface fddi0/0
  ip address yor.own.net.work your.mask.as.desired
  ip address bill.assigned.c.net secondary

end kludge;

If the box decides to send a ICMP message out on the interface
that faces the RA pirated network it will use the primary address, so
it will show up with the name and network number you prefer.