<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">2014-04-07 22:46 GMT+02:00 Sten Carlsen <span dir="ltr"><<a 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>On 07/04/14 22.23, alessandro macuz
wrote:<br>
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<div dir="ltr">2014-04-07 21:15 GMT+02:00 Simon Hobson <span dir="ltr"><<a href="mailto:dhcp1@thehobsons.co.uk" target="_blank">dhcp1@thehobsons.co.uk</a>></span>:<br>
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<div>alessandro macuz <<a 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>
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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>
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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>
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<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>
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<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
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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 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>