As a Network Engineer, I occasionally find myself trying to figure out reverse wildcard bits for Cisco router access lists. For some reason Cisco use these reverse wildcards instead of normal ones in ACLs.
That's fine, except I can never work them out in my head as I know the most basic ones by heart, the slightly less basic ones I can calculate in my head, but the tricky ones are a bit hard going.
This is a decent sized lashup consisting of G516,P20,S307,X34 and X33 + 44 hoppers, as it passed through Sunbury on the down at about 14:15 on 12 Feb, 2000.