This is actually the way NAT works, and it cannot work any other way. The
ICMP protocol cannot in any way keep track of which ping reply belongs to
which LAN computer in this situation. This is not FreeBSD-specific, but NAT
specific in general.
> On both the linux boxes, I run fping -c 1 -w 1 ns1.google.com
> ns1.yahoo.com www.ingateusa.com and sleep for 5 seconds. Basically they
> send simultaneous pings to three hosts once a second.
> Note that some packets are not getting NATted?
> This seems to be a bug in freebsd but I was wondering if anyone had any
> pointers to how to fix it?