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<div class="moz-cite-prefix">On 07/04/14 22.23, alessandro macuz
wrote:<br>
</div>
<blockquote
cite="mid:CAFrGbuW1hySdQiehW2mOS+uwq+FGtTx7Jz+EVbiCNnOybfF4MA@mail.gmail.com"
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:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="">alessandro macuz <<a
moz-do-not-send="true"
href="mailto:alessandro.macuz@gmail.com">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>
<blockquote class="gmail_quote" style="margin:0 0 0
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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>
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>
~~~~~~~~~~~~~~~~~~~~~<br>
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cite="mid:CAFrGbuW1hySdQiehW2mOS+uwq+FGtTx7Jz+EVbiCNnOybfF4MA@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">
<div>
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<div><br>
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<blockquote class="gmail_quote" style="margin:0 0 0
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<br>
For many clients (certainly the ISC one on Linux) you can
supply your own script/modify the stock one. That means
you can go and accept a lease, then use your own script to
fiddle with the system. Or at least I thin that's the
case.<br>
</blockquote>
<br>
</div>
<div class="gmail_quote">I thought of this and delete the 2nd
def route but even if for less than a second packets would
load-balanced between the two default routes. Now that I'm
writing I realize that the loadbalancing mechanism is in
place only when the adm distance is the same, so maybe I can
play with that value if the DHCP protocol allows that.<br>
<br>
</div>
<div class="gmail_quote">Alex<br>
</div>
</div>
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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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