When DHCP fails, ifup proceeds with trying to configure the
interface using the IPADDR from ifcfg-xxx file. I am not
sure if this is a good idea, but what's obviously wrong is
that it even does not check if IPADDR is not just "" (which
is quite likely when interface is set up ising DHCP). And
when IPADDR="", ifup starts calling various utilities
(ipcalc, ifconfig, etc) with bogus arguments and they start
printing various error messages.