binat rules

[^Beastie^]

Dear all 

I have problem to setup binat rule's on virtual interface's on pf.
the goal is to establishes a one to one mapping between an internal IP
address and an external addres.
this my partial configuration of rc.conf and pf.conf 

rc.conf :
ifconfig_bge2="inet 202.157.x.1 netmask 255.255.255.224"
ifconfig_bge2_alias0="inet 202.157.x.2  netmask 255.255.255.255"

pf.conf :
nat on bge2 from 172.16.0.0/16 to any -> 202.157.x.1
binat on bge2 from 172.16.0.25 to any -> 202.157.x.2


When this rule's apply, host 172.16.0.25 could not connect to internet.

Is there something wrong with my configuration ? please enlight me.

regards
Reza