Load balancing outgoing traffic

[Stefano Marinelli <postnet%dragas.dyndns.org@localhost>]

Hello everybody,
I've some Alix boards with NetBSD, working perfectly. At the moment, one of 
them is working as a network router/firewall (with ipfilter) between an ADSL 
ethernet modem and a lan. Nat is working, everything is right.
I've just discovered that, in that office, there's another (and faster) ADSL 
connection that is just used by one machine. So I was planning to do load 
balancing between the two connections to achieve better results. The Alix had 3 
network ports, so it could be perfect. After a short research, I've found out 
there's no way to do it with ipfilter (or is it possible?), but can be easily 
done with pf. So I loaded pf lkm (NetBSD 5.1) and started to play with it. 
Having used pf on some OpenBSD machines, I didn't have many problems to have a 
working firewall.
Then I found this link: http://www.openbsd.org/faq/pf/pools.html and found 
exactly what I was looking for. I copied and pasted the configuration they 
suggest (modifying the interfaces) into the pf.conf but when reloading pf, i 
get this error message:
/etc/pf.conf:9: syntax error

the line number nine is this: 
match out on $ext_if1 from $lan_net nat-to ($ext_if1)

so it seems NetBSD's pf is having troubles with it.

Any suggestion?

Thanks,
Stefano