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I just moved from the RIP chapter to EIGRP in the course and I'm a bit confused. RIP was simple — count the hops, lowest wins, max 15. But EIGRP apparently uses this composite metric with bandwidth and delay (and load/reliability?) and I don't really get why it's more complicated.

What problem does bandwidth + delay actually solve that hop count doesn't? And when EIGRP picks a path, which one "wins" — the fewest hops or something else? Trying to build the right mental model before I do the lab. 🙂

I learned that standard ACLs should go near the destination and extended ACLs near the source. But why? If the ACL blocks traffic either way, what difference does placement make? Can someone explain with a concrete example?

I can configure both static routes and default routes on a router. But when should I use a specific static route pointing to a network vs just a default route that catches everything? Is there a best practice for small networks vs large ones?

I know TTL decrements at each hop but what exactly happens when it hits zero? Does the packet just disappear? Does the router send something back? And how does this relate to traceroute? I've seen TTL mentioned in ping output but never really understood the mechanics.