Traffic Shaping Bridge with Dummynet

Dan D Niles dan at
Mon Sep 14 19:13:21 UTC 2009

I am trying to do traffic shaping using a bridge on FreeBSD 7.1.

I have the bridge configured and it works fine.  It looks like this:

rest of network <-> xl0 <-> bridge0 <-> xl1 <-> side to be shaped

It works with the following set of ipfw rules (pipes in but 
unlimited bw):

	ipfw -q -f flush

	ipfw -q pipe 1000 config mask dst-ip 0x000000ff bw $limit
	ipfw -q add pipe 1000 ip from any to $network via xl1

	ipfw -q pipe 1001 config mask src-ip 0x000000ff bw $limit
	ipfw -q add pipe 1001 ip from $network to any via xl1

	ipfw -q add 60000 allow all from any to any

If I change the limit to 1Mbit/s (or anything else) it stops passing
traffic.  I used tcpdump and I can see the traffic on the bridge but I
cannot see it after the bridge.  However "ipfw -a list" shows the counts
for the pipe going up, which doesn't make sense to me.

I've tried adding:
	ipfw -q add allow all from any to any via bridge0
	ipfw -q add allow all from any to any via xl0
before the pipes.  I also tried moving the pipes to bridge0 and xl0.

The docs on bridging
says "The bridge can be used as a traffic shaper with altq(4) or

So what am I doing wrong?  What else do I need to do to limit the
bandwidth over a bridge?



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