FreeBSD deny 'unusual' IP-addresses?

[Васенин Александр aka BlackSir]

I work in a small ISP company. We are using FreeBSD machines for routing and
counting traffic of our clients. I faced with subject 'feature' twise:

1) FreeBSD Server with a real ip in external interface and a lot of IPs like
10.1.1.1/24, 172.16.13.1/24 (NOT ANY 192.168...!)on internal interface. If
someone tries to up an ANY address like 192.168.0.1/24 - our server always
talk that this address is already in use. Those clients need these
addresses, becouse they use our LAN as transport beetween two offices. I
solved this problem by upping 192.168.1.1/16 on internal server interface .

2) One of our client use our LAN for testing their experimental hardware
device (i don`t know what that thing do, but in connected to network). For
some unknown reason that device use a real IP-address that not belongs to
me, but they don't want to change the address(why? - I don't know). Our
server swears that this address is already in use.

I understand, that using such thing is not compliant to standarts, but maybe
someone knows how to switch off those kind of alarms?
	Vasenin Alexander aka BlackSir