Untangle is another open source model that I can refer. It is really good, easy to use and rich in features. Yes, for few of the advanced modules you may need to pay or do your customization on your own, but in general it is a good model to review for your firewall-engineering.
MVP (Enterprise Security), ISLA-2010 (ISC)², C|EH, C|HFI, CCNA, MCP,
Certified ISO 27001:2005 Lead Auditor
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