Standard vs extended ACL — when do you use each?

Standard ACL (1–99 or 1300–1999) — filters by source IP only. Apply close to destination (because filtering only by source means you don't want to block legitimate traffic to other destinations from same source). Extended ACL (100–199 or 2000–2699) — filters by source IP + destination IP + protocol + ports. Apply close to source for efficiency (drops unwanted traffic before it traverses the network). Modern best practice: use named ACLs for both readability.

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ACLs / NAT

Q. Difference between NAT, PAT, and dynamic NAT?

NAT (static) — 1:1 mapping between inside-local and inside-global. Used for servers needing fixed external IPs. Dynamic NAT — pool of inside-global IPs assigned dynamically to inside-local IPs as needed. Once mapping est…

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