ipfw + dummynet: bandwidth limiting not working

[Jason Kocol]

I am running FreeBSD 4.8 STABLE and am trying to use dummynet with ipfw to
limit bandwidth on my DSL connection.  I have added the rules for dummynet
to my existing firewall rules in rc.firewall (which are pretty open as you
can see) in the last two lines below:

ipfw -f flush
ipfw add divert natd all from any to any via vx0
ipfw add pass all from any to any
ipfw pipe 1 config bw 128K
ipfw add pipe 1 tcp from x.x.x.x to any

(x.x.x.x being my public IP address, and vx0 in line 2 being the interface
for this address)

By those last two lines I would expect the outbound/inbound traffic to be
limited to 128Kbps, yet I am still able to transfer data at my normal
broadband speeds (1.5Mb/768Kb).

Anyone have any idea why this is not working the way I'd expect it to?

Thanks,
-Jason