pg_hba.conf is inscrutable to me

Hello all.  I hope this is the right place for this question.  On a
machine called falstaff.trgrdc.mc.xerox.com, IP address 13.137.84.27,
I've got the following pg_hba.conf:

local        all                                            trust
host         all         13.137.84.27     255.255.255.255   trust
host         all            127.0.0.1     255.255.255.255   trust
host         all              0.0.0.0             0.0.0.0   trust

While logged on to this machine as UID postgres, I do the following:

psql -h falstaff.trgrdc.mc.xerox.com

... and get the following message:

Connection to database 'postgres' failed.
No pg_hba.conf entry for host 13.137.84.27, user postgres, database
postgres

... tried lots of variations on the pg_hba.conf, none of which worked.
I can't see what's wrong with this one.  Any
suggestions?

--
Robert Miller
The Rochester Group
600 Park Avenue
Rochester, NY 14607

I will say one thing.  It is amazing how many drivers, even at the
Formula One level, think that the brakes are for slowing the car down.
                                                Mario Andretti