I have PIX 520 that I want to replace, I assume the new replacement is ASA. My question is which model. I use the PIX simply as a firewall. I do not want to under-engieenr the solution. So I will probably will require min three interfaces inside, outside and DMZ.
Bellow pdf provides migration guide from PIX 500 series to ASA5500 series.
PIX520 equivalent upgrade to asa is asa5520 but from what you have indicated needing only inside,outside and DMZ you probably are looking at the ASA5510, you still need to conduct thourough assesment and baseline of your currently PIX520 such Ipsec vpns tunnels currentl utilization if any, look at bellow comparison table and total ASA firewall Mbps throughput.
There are number of tools out there, pdm has a built-in monitoring tool tab which you can use to monitor pix cpu usage, xlate , regular connections, Ipsec connections etc.. you could setup graphical monitoring and let it run for a week to sort of get you overall pix utilization baseline.
You could also use PRGT to monitor the physical ports ethernet utilization, example would be the inside interface connecting to a switchport , monitor switchport through PRTG.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...