I am sharing here links on where to find free/paid network security appliance images for GNS3 or other network emulation software such as Eve-NG.
GNS3 may be a free emulation tool, but it does not come with binary images for appliance such as that of Cisco, Palo Alto, Fortinet. Due to licensing restrictions, you or your organization needs to have a service contract agreement with the vendor.
1. GNS3 Marketplace
One of the first place to check is the GNS3 Marketplace where you can search for images which may have links going to external vendor sites. Please not that other vendors may still need pre-existing service contract between you and your organization to get access to the downloadable binary image. Other vendors (e.g. Cumulus) may provide free images without this restriction.
2. Cisco VIRL and Download Center
Before considering downloading images and an emulation software, check out Packet Tracer first. If your prepping for your CCNA, the free Packet Tracer Simulation software is more than enough.
On the other hand, if your prepping for CCNP CCIE or setting up a network security emulation to scale, then Cisco Download Center or VIRL (Virtual Internet Routing Lab) are viable options. You need to setup a free account with Cisco. However, VIRL is a paid service (e.g. USD 199/year subscription). With a VIRL subscription, you can download VIRL images for various network appliances. Currently, downloadable Firepower FTD images are not part of the VIRL. To get access to the download center files, you or your organization needs to have service contract agreement with Cisco.
3. Palo Alto Appliance Downloads
For quick run-up to test a feature with Palo Alto NGFW, one quick option would be the Palo Alto VM bundle packages at the AWS Marketplace ( ~1.572USD/hr, pay as you go). For Palo Alto VM/OS Images you can go to PA-VM Appliance Download page. You can also register with PA Customer Support to get a free evaluation version.
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