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[dil]

Внезапно:
Q. What operating system is the ASA built on?
A. Cisco ASA Software runs on Linux as an ASA OS process. Cisco ASA Software is not forked off Cisco IOS® Software. Its roots are in the Cisco Finesse ® OS (an embedded OS), which ran on older Cisco PIX® firewall platforms.

Оригинал этой записи в личном блоге.