For practice exams, Boson ExSim is excellent, but you need to purchase it legally. Many employers will reimburse study materials, and Boson sometimes offers student discounts.

If you're looking for free or low-cost study resources, consider:

Cracked installers are frequently infected with Trojans, ransomware, or keyloggers that can steal your passwords and financial data.

If the official Boson NetSim is outside your budget, these tools are widely used by the CCNA community: