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.