The following error message occurs in NGDBuild:
"ERROR:NgdBuild:755 - Line xx in '<file>.ucf': Could not find net(s) '<X>' in the design. To suppress this error use the -aul switch, specify the correct net name or remove the constraint."
To prevent this error, ensure that the name listed in the constraints file or in the related EDIF file matches the top-level netlist file name.
ngdbuild -aul design.edn design.ngd
This option can also be selected in the Project Navigator under the Translate options. The corresponding ISE property is "Allow Unmatched LOC Constraints." In ISE 5.x, this is an Advanced property.
If you are trying to preserve any external ports that are not yet connected internally, Xilinx recommends that you use the "-aul" switch in NGDBuild (ngdbuild -aul design.edf design.ngd) to pass through implementation and use the PROHIBIT constraint on the unused pad sites.