I'm studying for a Cisco exam (CCNA). I already have Cisco's Packet Tracer software (which you can get for free). My exam book further provides a free version of the Pearson Network Simulator Lite and something called Config Labs, however it says that this will be insufficient to prepare for the exam. The book recommends, at a minimum, the Virtual Internet Routing Lab (VIRL).
Since my career is in mathematical sciences and I'm just getting into this out of personal interest, thinking maybe I can apply my skillset to a networking context afterwards, this is all self funded. Between the books, video lectures, and exam fees, I'm all tapped out.
Is there a good free alternative to VIRL and/or other relevant Cisco products (like their virtual learning labs, Cisco CCNA Routing and Switching 200-125 Network Simulator, the full version of Pearson Network Simulator, etc).