I have a melon scratcher ...   I have two m0n0wall boxes that are
almost identically configured as front ends to a voip system and
general internet access. One has a cable feed, the other DSL, though
for a while they both had DSL (and I still had the same problem).

If I run the magic traffic shaper on one box and then add the two
extra rules given below, then it all works (wonderfully!) as expected.
The voip traffic on the OPT2 interface never misses a beat whatever we
do on the LAN interface (eth1).

However, if I do the same thing on the other box, it immediately stops
passing traffic to or from the WAN port - until I call someone onsite
and have them disable the traffic shaper. Even simple stuff like pings
stop responding.

I've got to the point of diff'ing the two XML files (finding nothing
obvious) and have searched the archives and found one cryptic
reference to an MTU solution - but I'm not using PPPoE anywhere.

Anyhow, I hope things rings a bell for someone...

		<rule>
			<interface>wan</interface>
			<source>
				<network>opt2</network>
			</source>
			<destination>
				<any/>
			</destination>
			<direction/>
			<iplen/>
			<iptos>lowdelay,throughput,reliability,mincost,congestion</iptos>
			<tcpflags/>
			<descr>Voip priority for pbx</descr>
			<targetpipe>0</targetpipe>
		</rule>
		<rule>
			<interface>wan</interface>
			<source>
				<network>opt2</network>
			</source>
			<destination>
				<any/>
			</destination>
			<direction/>
			<iplen/>
			<iptos>lowdelay,throughput,reliability,mincost,congestion</iptos>
			<tcpflags/>
			<descr>Voip priority for pbx</descr>
			<targetpipe>1</targetpipe>
		</rule>

In case it matters, this is a 5 ethernet port Soekris 4801 with WAN,
LAN, Voip LAN and a 4th port bridged to WAN to put the Asterisk box
itself on a separate (firewalled) IP (5th port is currently unused,
most likely will have an AP attached at some future time).

thanks in advance!  michael