If you use 2x/3x spacing in your design.ctstch to get the extra spacing for xtalk prevention, you might not get what you want if your design is too congested. Since those rule are soft constrain, Nanoroute will try it best to follow it if possible. To be sure you are getting the 2x/3x spacing, you need to create a NONDEFAULT rule in your lef file and specify it in your design.ctstch before you run CTS.Originally posted in cdnusers.org by lisiang
You also need to add the following before the clock routing.
setNanoRouteMode routeStrictlyHonorNonDefaultRule true