network routing, strange issue

[dave]

Hello,
    I've got three FreeBSD machines, a 4.9, and two 4.7 boxes. They're on a
small local network with a hub. Each is given an IP statically via dhcp
based on their nic mac address. All machines obtain a dhcp lease, machines a
and c can ssh and ping each other and have no issues. My problem is machine
a can not ping or ssh to machine b, from machine a's point of view it's as
if machine b doesn't exist, yet machine c has no difficulties interacting
with machine b. I hope the above made sense. Any help appreciated.
Thanks.
Dave.