<div dir="ltr"><div class="gmail_extra"><div><div class="gmail_signature"><br></div></div><div class="gmail_quote">On Wed, Jun 24, 2015 at 12:38 PM, Leandro <span dir="ltr"><<a href="mailto:ingrogger@gmail.com" target="_blank">ingrogger@gmail.com</a>></span> wrote:<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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Simon , Bob , Peter:<br>
Thank for sharing your wisdom on this, there is something I still
can not understand.<br>
Maybe a picture can help, please take a look bellow.<br>
On scenario 1 following should happend:<br>
Relay1 will set Gi-addr=1.1.0.1 so dhcpd will pick a lease from pool
1 and network <a href="http://1.1.0.0/24" target="_blank">1.1.0.0/24</a> will use 1.1.1.1 as gateway.<br>
Relay2 will set Gi-addr=1.1.2.1 so dhcpd will pick a lease from pool
3 and network <a href="http://1.1.2.0/24" target="_blank">1.1.2.0/24</a> will use 1.1.2.0 as gateway.<br>
This is ok;<br>
<br>
On Scenario 2<br>
After running out of /24 ips I will add remaining /24 networks
behind each relay.<br>
Add pool2 behind relay 1<br>
Add pool4 behind relay 2.<br>
How will it work ? <br>
My concern is that, if relay1 still using 1.1.0.1 for gi-addr ;
dhcpd can pick a lease from pool4 instead using pool2 since 1.1.0.1
falls into the <a href="http://1.1.0.0/22" target="_blank">1.1.0.0/22</a> declared on shared network.<br>
If this happens the request will receive the option router = 1.1.3.1
witch ip is not set at any interface on relay1.<br>
And vice-versa, dhcp server can pick a lease from pool2 for a
request coming from relay2, so it will also receive an incorrect
router value.<br><div><div class="h5"><br></div></div></div></blockquote><div><br></div><div>You need separate shared networks:</div><div><div>shared-network sitea {</div><div><span class="" style="white-space:pre"> </span>subnet 1.1.0.0 ...</div><div><span class="" style="white-space:pre"> </span>...</div><div><span class="" style="white-space:pre"> </span>subnet 1.1.1.0 ...</div><div><span class="" style="white-space:pre"> </span>...</div><div>}</div><div><br></div><div>shared-network siteb {</div><div><span class="" style="white-space:pre"> </span>subnet 1.1.2.0 ...</div><div><span class="" style="white-space:pre"> </span>...</div><div><span class="" style="white-space:pre"> </span>subnet 1.1.3.0 ...</div><div><span class="" style="white-space:pre"> </span>...</div><div>}</div></div><div><br></div><div> </div><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"><div bgcolor="#FFFFFF" text="#000000"><div><div class="h5">
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<div>On 23/06/15 18:19, Simon Hobson wrote:<br>
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<pre>Leandro <a href="mailto:ingrogger@gmail.com" target="_blank"><ingrogger@gmail.com></a> wrote:
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<pre>After I run out of those ips, I can do two thinks:
a)change the network mask from /24 to /23.
b)Add a second /24 subnet behind the relay , for example <a href="http://1.1.2.0/24" target="_blank">1.1.2.0/24</a> and set a second gateway ip <a href="http://1.1.2.1/24" target="_blank">1.1.2.1/24</a>.
option a) is not good since the broadcast domain at /23 could bring many collisions. (its just my opinion).
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<pre>I don't think it will make much difference. Don't forget that having two subnets in a shared network won't segregate the broadcast traffic. I think the only reduction would be from inter subnet traffic going via the router rather than using ARP to find the neighbour - but routing the traffic via the router rather than directly will more than outweigh any saving there.
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<pre>option b) Could work but, how does relay agent knows witch ip to use for GI-Adrr ?
Can relay agent send both or more than one ips, on the GI-Addr field so dhcpd can figure out from witch range can serve the ip ?
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<pre>As already mentioned, as long as the GI-Addr value is within any of the subnets, then the server will work it out from the shared-network.
BTW - I'd suggest a read of "The DHCP Handbook" by Ralph Droms and Ted Lemon, it explains all this and a lot more, and is quite readable.
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