0&0xa006402      255.255.0.0       UGS         0    14513      -  fxp0 =>

That appears to be a route with a non-normal mask, where the
destination is 0.0.0.0, but the mask is 10.0.100.2.
This was likely created with
route add default -netmask 10.0.100.2 255.255.0.0

I ran that and ping of 1.0.0.0 (note that this has no bits set which
are in the match) gave me the same kernel msg:
arpresolve: can't allocate llinfo on fxp0 for 255.255.0.0

# route delete default -netmask 10.0.100.2

removed the bogus route.

I would recommend kevlar engtex chaps when playing with non-normal
routes:
   http://www.stihlusa.com/apparel/protect_chaps.html

But seriously, I wonder if a sysctl to allow non-normal masks is in
order, defaulting to not allowed.

-- 
        Greg Troxel <gdt@ir.bbn.com>