Which platform?
In Windows based, you should use different tools to cover the design flow: ModelSim (simulation), Leonardo (synthesis), Ledit (layout generation). But the biggest problem is related to layout generation, because it does not support efficient algorithms to do automatic routing.
In Linux based, you can use Cadence packages (IC5.0.33, SOC 3.3, LDV and ICC) which cover the design flow completely. To generate layout for large design, you have to use SUN system instead of PC.
Regards,
KH