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Just a thought:<br>
<br>
Did you consider to let the DHCP server send the correct gateway?
Would that solve the issue?<br>
<br>
<div class="moz-cite-prefix">On 08/04/14 15.03, alessandro macuz
wrote:<br>
</div>
<blockquote
cite="mid:CAFrGbuX67PHoss0Td5g27FuN3-TULrK8diOFk+opKM9r_AsZ-Q@mail.gmail.com"
type="cite">
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<div class="gmail_extra">
<div class="gmail_quote">2014-04-07 22:46 GMT+02:00 Sten
Carlsen <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:stenc@s-carlsen.dk" target="_blank">stenc@s-carlsen.dk</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
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<div class=""> <br>
<div>On 07/04/14 22.23, alessandro macuz wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">2014-04-07 21:15 GMT+02:00 Simon
Hobson <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:dhcp1@thehobsons.co.uk"
target="_blank">dhcp1@thehobsons.co.uk</a>></span>:<br>
<div class="gmail_extra">
<div class="gmail_quote">
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
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<div>alessandro macuz <<a
moz-do-not-send="true"
href="mailto:alessandro.macuz@gmail.com"
target="_blank">alessandro.macuz@gmail.com</a>>
wrote:<br>
<br>
> I could deduce the gateway from the
DHCP server IP address because normally
they coincide but that would be my
assumption.<br>
<br>
</div>
You've heard the expression that "assume"
makes an "ass" out of "u" and "me", well
your assumption is badly wrong. In home and
small networks it is likely to be true (not
mine though). But once you get to business
networks then its more likely that the DHCP
server is not at the same IP address as the
router.<br>
</blockquote>
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style="margin:0px 0px 0px
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However, I'm still not quite sure why you
are doing things the long way round. What's
specifically wrong with using the route that
comes with the lease ? Or more to the point,
what's wrong with dealing with it when you
get it ? And BTW - have you considered the
possibility of getting different answers to
your two queries ?<br>
</blockquote>
<div><br>
</div>
<div>Sorry maybe I should have added more
details but there is only one defaut gateway
on the network of that interface and hence
the dry-run returns always the same IP
address. As to the second reply it will
configure the interface.<br>
<br>
</div>
<div>Why I want to run a dry-run? Because
eventually I need to install some routes
pointing to the only gateway on the network.
On the system there is another interface
that gets the IP dinamically and two default
routes are not OK <br>
</div>
</div>
</div>
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</blockquote>
</div>
I suggest you look at: /sbin/dhclient-scripts<br>
<br>
It contains the following code, I think a small
modification to this will do your job:<br>
~~~~~~~~~~~~~~~~~~~~~<br>
add_default_gateway() {<br>
router="${1}"<br>
<br>
if is_router_reachable ${router} ; then<br>
metric=""<br>
if [ $# -gt 1 ] && [ ${2} -gt 0 ]; then<br>
metric="metric ${2}"<br>
fi<br>
ip -4 route replace default via ${router} dev
${interface} ${metric}<br>
if [ $? -ne 0 ]; then<br>
logmessage "failed to create default route:
${router} dev ${interface} ${metric}"<br>
return 1<br>
else<br>
return 0<br>
fi<br>
fi<br>
<br>
return 1<br>
}<br>
</div>
</blockquote>
<div><br>
</div>
<div><br>
</div>
<div>Thanks Sten,</div>
<div><br>
</div>
<div>I don't see such <font face="arial, sans-serif">add_default_gateway()
function in my Ubuntu 12.04.4 but I do see</font><br>
<br>
<div><font face="arial, sans-serif"> for router
in $new_routers; do</font></div>
<div><font face="arial, sans-serif"> if [
"$new_subnet_mask" = "255.255.255.255" ]; then</font></div>
<div><font face="arial, sans-serif"> #
point-to-point connection => set explicit route</font></div>
<div><font face="arial, sans-serif"> ip
-4 route add ${router} dev $interface >/dev/null
2>&1</font></div>
<div><font face="arial, sans-serif"> fi</font></div>
<div><font face="arial, sans-serif"><br>
</font></div>
<div><font face="arial, sans-serif"> # set
default route</font></div>
<div><font face="arial, sans-serif"> ip -4
route add default via ${router} dev ${interface} \</font></div>
<div><font face="arial, sans-serif">
${metric_arg} >/dev/null 2>&1</font></div>
<div><font face="arial, sans-serif"> done</font></div>
<div style="font-family:arial,sans-serif;font-size:13px">
<br>
</div>
</div>
<div><span
style="font-family:arial,sans-serif;font-size:13px">when
$reason is set to </span><font face="arial, sans-serif">BOUND
or RENEW or REBIND or REBOOT or TIMEOUT.</font></div>
<div><font face="arial, sans-serif"><br>
</font></div>
<div><font face="arial, sans-serif">Eventually I realized I
have access to the DHCP server (openwrt) and the trick
may be not to send the default route and at the same
time to use the option 121 (client must explicitly
request it)</font></div>
<div><font face="arial, sans-serif"><br>
</font></div>
<div><font face="arial, sans-serif"><a
moz-do-not-send="true"
href="http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2006q2/000818.html">http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2006q2/000818.html</a><br>
<br>
I'll give it a try.</font></div>
<div><font face="arial, sans-serif"><br>
</font></div>
<div>Alex<br>
</div>
</div>
</div>
</div>
<br>
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</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Best regards
Sten Carlsen
No improvements come from shouting:
"MALE BOVINE MANURE!!!"
</pre>
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