Cisco Adaptive Security Appliance, the stateful firewall platform that has anchored enterprise perimeters for two decades and is now being succeeded by Secure Firewall (FTD). Articles tagged ASA cover security levels, NAT 8.3+ and twice NAT, ACLs, AnyConnect SSL and IKEv2 VPN, site-to-site IPsec, failover, packet-tracer, hardening, and ASAv 9.x lab walkthroughs.
The outbound NAT rule almost every ASA runs: dynamic PAT to the outside interface IP. This post covers the exact configuration on a real ASAv, the show commands that prove it works, and the failure modes you will eventually see.
Configure site-to-site IPsec on the Cisco ASA the way 90 percent of production tunnels run today: IKEv2 with crypto maps, plus a section on route-based VTI for engineers who want the route-aware model.
Every ASA interface gets a security level from 0 to 100, and default forwarding between interfaces is decided entirely by that number. This article covers the convention, the same-security cases, and the day-one mistakes.
ASA ACLs apply inbound, match the real untranslated destination IP, and lean on object groups for readability. This article walks the full model, the syntax, and the mistakes engineers coming from IOS hit on day one.
Every packet crossing an ASA hits a deterministic series of checks: interface ACL, NAT, route lookup, and more. Walk all nine steps on software 9.x with a worked lab example, pinned to the config block you inspect when each step fails.
ASA NAT changed completely in software 8.3, and old documentation still teaches the wrong model. This guide covers the modern one: Auto NAT vs Manual NAT, how they differ, and the order the ASA evaluates them.
packet-tracer simulates one packet through every ASA decision point, NAT, ACL, and route lookup included, and tells you exactly where it would be dropped. Covers the syntax, the common scenarios, and how to read each phase of the output.
A working Cisco ASA cheat sheet: show version, write memory, failover, ACLs, NAT, and the troubleshooting commands you actually reach for under pressure.
The Cisco ASA does not run CDP. Here is why, how to find the ASA from the connected switch with CDP, LLDP and the MAC table, and what to run on the ASA itself.