Enabling Router blocks

Ah - I see the problem. I misinterpreted:

>> However, when I start bro I get error: can't open drop.

to mean it was coming from the shell. But it's coming from Bro. There
isn't any policy script called drop.bro, so it's telling you that "@load
drop" failed.

You turn on address dropping by

  @load scan
  redef can_drop_connectivity = T;

and redefining "drop_connectivity_script" (which it sounds like you've
already done).