address under test: 104.20.23.154  (inside 104.16.0.0/12, outside 172.64.0.0/13)

of("104.16.0.0/12")                                            -> true
of("104.16.0.0/12", "172.64.0.0/13")                           -> true

externalAddresses().and("104.16.0.0/12")                       -> true
externalAddresses().and("104.16.0.0/12", "172.64.0.0/13")      -> false
externalAddresses().and(of("104.16.0.0/12", "172.64.0.0/13"))  -> true

The fourth line is the trap. One address is one filter; two addresses
are two filters ANDed, and no address is inside two disjoint ranges.