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<p class=MsoNormal><span style='color:#1F497D'>Boy am I tired! And a
little embarrassed. But glad I can get some sleep now. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Turns out, the problem was a
dumb firewalling on my part. After dropping my filter rules and trying
bazillions of different combinations, one time I re-ran my rc.firewall script
and one ping happened to sneak through. My script template sets the
default policy to ACCEPT at the top and then sets it to DROP at the end. The
idea is to reduce the probability that a typo in a script will force me to jump
in the car and drive somewhere in the middle of the night. So one ping
was able to sneak through while it was open. That was maybe 7 or 8 hours
ago, I have a hard time remembering. I should have paid more attention –
this would have saved me lots of grief. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Anyway, after spending all day
studying all kinds if ip xfrm commands, I decided to completely drop **all**
firewall rules, including all the NAT rules. I did it safely, like this:<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>./allow-all && sleep 10
&& ./rc.firewall norestartservices<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>And during those glorious 10
seconds, echo requests and replies made a round trip. So it **HAD** to be
my rules. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>With pings running in one window
and watching the counters using iptables –L –v –n –t nat
in another window, I noticed I was MASQUERADEing about one packet every
second. Hmmmm, about the same rate as my inbound pings. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Putting in a temporary logging rule
to show me everything masqueraded, I was shocked to find I was masquerading
packets coming FROM Rochester and branch sites. I had some POSTROUTING
rules to ACCEPT everything TO Rochester, but nothing for packets FROM
Rochester. It all makes sense now – and maybe this writeup will be
helpful for the next person who stumbles into my mistake and will save 14,
count ‘em, 14 solid hours of troubleshooting. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Here is the lesson: If you’re
bridging and the network behaves strangely, for your very first troubleshooting
step, log what you masquerade first and make appropriate adjustments. This
may save you several hours and prevent a headache.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='color:#1F497D'><span style='mso-list:Ignore'>-<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='color:#1F497D'>Greg Scott<o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
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