One question that comes up several times a week is "how many ISA firewalls do I need and how ’big’ do they need to be"?
To be more specific, the questions are I hear and see go along these lines:
- "I have 5000 remote access VPN users. How many ISA firewalls do I need and how big do those boxes have to be
- "I have 10,000 OWA users. How many ISA firewalls do I need and how big do those boxes have to be
- "I have 15,000 users on my corporate network, how many ISA firewalls do I need and how big do those boxes need to be
These are valid questions. While there is an excellent ISA firewall performance best practices white paper over at http://www.microsoft.com/technet/prodtechnol/isa/2...s.mspx there is a bit of a learning curve to understanding how to apply that white paper to an actual deployment and busy network admins and sales staff tend to shy away from that kind of work.
To solve this problem, Microsoft has come up with an ISA firewall sizing calculator. You can find it on the ISA firewall landing page over at www.microsoft.com/isaserver and it’s part of the flash content at the top of the page.
Let me know what you think of the calculator. I’m particularly interested in whether or not you think the sizing calculator answers the question above and if it answers any other specific question you have for you own ISA firewall deployment. Just post your responses to this blog post and I’ll make sure they get to the right people at Microsoft.