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<div>I didn't go over your config with a fine toothed comb, but one thing that's glaring, is that static assignments must be outside any range. I know this seems a little counter-intuitive, and I struggled with it years ago, but that's how it's got to be.</div>
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<div class="BodyFragment"><font size="2">
<div class="PlainText">-G<br>
<br>
/*<br>
* Glen R. J. Neff<br>
* USD Lab Operations Infrastructure Team<br>
* glen.neff@emc.com<br>
*<br>
* EMC^2 == E^2<br>
*/</div>
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<font color="#000000" size="2" face="Tahoma"><b>From:</b> dhcp-users-bounces+glen.neff=emc.com@lists.isc.org [dhcp-users-bounces+glen.neff=emc.com@lists.isc.org] On Behalf Of Turnpaugh , George [George.Turnpaugh@arrisi.com]<br>
<b>Sent:</b> Tuesday, October 15, 2013 4:51 PM<br>
<b>To:</b> dhcp-users@lists.isc.org<br>
<b>Subject:</b> Static and dynamic DHCP across shared networks<br>
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<p class="MsoNormal"> </p>
<p class="MsoNormal">We're trying to create a dhcpd.conf file for multiple sub-networks such that we can control IP address assignment for cable modems and CPE’s connected to these cable modems.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">Each sub-network contains several host entries, each with a fixed IP address. (These are for the cable modems.)</p>
<p class="MsoNormal">Each sub-network is configured as a /19 network.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">All of the sub-networks are contained within a "shared-network" clause.</p>
<p class="MsoNormal">The first sub-network is considered the default network.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">An example of our dhcpd.conf file is shown below.</p>
<p class="MsoNormal">We found that the "shared-network" statement is needed to get the specified fixed addresses to be handed out, otherwise only addresses from within the first sub-network are picked.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">shared-network MVRF1 {</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> # Subnet 1</p>
<p class="MsoNormal"> subnet 10.106.0.0 netmask 255.255.224.0 {</p>
<p class="MsoNormal"> range 10.106.0.255 10.106.31.254;</p>
<p class="MsoNormal"> option subnet-mask 255.255.224.0;</p>
<p class="MsoNormal"> option broadcast-address 10.106.31.255;</p>
<p class="MsoNormal"> option routers 10.106.0.1;</p>
<p class="MsoNormal"> }</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> # Subnet 2</p>
<p class="MsoNormal"> subnet 10.106.32.0 netmask 255.255.224.0 {</p>
<p class="MsoNormal"> range 10.106.32.255 10.106.63.254;</p>
<p class="MsoNormal"> option subnet-mask 255.255.224.0;</p>
<p class="MsoNormal"> option broadcast-address 10.106.63.255;</p>
<p class="MsoNormal"> option routers 10.106.32.1;</p>
<p class="MsoNormal"> }</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> # Subnet 3</p>
<p class="MsoNormal"> subnet 10.106.64.0 netmask 255.255.224.0 {</p>
<p class="MsoNormal"> range 10.106.64.255 10.106.95.254;</p>
<p class="MsoNormal"> option subnet-mask 255.255.224.0;</p>
<p class="MsoNormal"> option broadcast-address 10.106.95.255;</p>
<p class="MsoNormal"> option routers 10.106.64.1;</p>
<p class="MsoNormal"> }</p>
<p class="MsoNormal">}</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">#Vrf_Default</p>
<p class="MsoNormal">group {</p>
<p class="MsoNormal"> host modem10 {</p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:1b:63;</p>
<p class="MsoNormal"> fixed-address 10.106.1.20;</p>
<p class="MsoNormal"> filename "basic.bin";</p>
<p class="MsoNormal"> }</p>
<p class="MsoNormal"> host modem11 {</p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:1b:60;</p>
<p class="MsoNormal"> fixed-address 10.106.1.21;</p>
<p class="MsoNormal"> filename "basic.bin";</p>
<p class="MsoNormal"> }</p>
<p class="MsoNormal">}</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">#Vrf_A</p>
<p class="MsoNormal">group {</p>
<p class="MsoNormal"> host modem20 {</p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:1c:8c;</p>
<p class="MsoNormal"> fixed-address 10.106.33.20;</p>
<p class="MsoNormal"> filename "basic.bin";</p>
<p class="MsoNormal"> }</p>
<p class="MsoNormal"> host modem21 {</p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:1c:ce;</p>
<p class="MsoNormal"> fixed-address 10.106.33.21;</p>
<p class="MsoNormal"> filename "basic.bin";</p>
<p class="MsoNormal"> }</p>
<p class="MsoNormal">}</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">#Vrf_B</p>
<p class="MsoNormal">group {</p>
<p class="MsoNormal"> host modem30 {</p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:20:61;</p>
<p class="MsoNormal"> fixed-address 10.106.65.20;</p>
<p class="MsoNormal"> filename "basic.bin";</p>
<p class="MsoNormal"> }</p>
<p class="MsoNormal"> host modem31 {</p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:14:8b;</p>
<p class="MsoNormal"> fixed-address 10.106.65.21;</p>
<p class="MsoNormal"> filename "basic.bin";</p>
<p class="MsoNormal"> }</p>
<p class="MsoNormal">}</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">There are two problems we're trying to find a solution to:</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">1. When a cable modem WITHOUT a fixed address registers, the DHCP server dynamically hands out the highest free address from the "highest address shared sub-network".</p>
<p class="MsoNormal">In the above example, it's from sub-network 10.106.64.0, (for example 10.106.64.254).</p>
<p class="MsoNormal">The address handed out is NOT from the first sub-network defined (10.106.0.0), which is our default sub-network.</p>
<p class="MsoNormal"> </p>
<p class="MsoListParagraph" style="MARGIN-LEFT: 24.75pt; TEXT-INDENT: -0.25in"><span>-<span style="FONT: 7pt 'Times New Roman'">
</span></span>Is there a way to specify which sub-network addresses are picked from for dynamic hosts within a shared network space.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">2. When CPE's connected to a cable modem request DHCP, they also end up getting an address in the same way described above,</p>
<p class="MsoNormal">they get the highest free address from the "highest address shared sub-network".</p>
<p class="MsoNormal">This occurs even though the relay agent address (for example 10.106.32.1, as verified by Wireshark) is an address from within the sub-network upon which the modem is registered.</p>
<p class="MsoNormal"> </p>
<p class="MsoListParagraph" style="MARGIN-LEFT: 24.75pt; TEXT-INDENT: -0.25in"><span>-<span style="FONT: 7pt 'Times New Roman'">
</span></span>Is there a way to have the DHCP server dynamically hand out a free address from within the sub-network upon which the modem is registered.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">Thanks in advance for anyone who may have knowledge in this area,</p>
<p class="MsoNormal">G. Turnpaugh</p>
<p class="MsoNormal"> </p>
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