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<p class="MsoNormal"><o:p> </o:p></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.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Each sub-network contains several host entries, each with a fixed IP address. (These are for the cable modems.)<o:p></o:p></p>
<p class="MsoNormal">Each sub-network is configured as a /19 network.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">All of the sub-networks are contained within a "shared-network" clause.<o:p></o:p></p>
<p class="MsoNormal">The first sub-network is considered the default network.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">An example of our dhcpd.conf file is shown below.<o:p></o:p></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.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">shared-network MVRF1 {<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> # Subnet 1<o:p></o:p></p>
<p class="MsoNormal"> subnet 10.106.0.0 netmask 255.255.224.0 {<o:p></o:p></p>
<p class="MsoNormal"> range 10.106.0.255 10.106.31.254;<o:p></o:p></p>
<p class="MsoNormal"> option subnet-mask 255.255.224.0;<o:p></o:p></p>
<p class="MsoNormal"> option broadcast-address 10.106.31.255;<o:p></o:p></p>
<p class="MsoNormal"> option routers 10.106.0.1;<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> # Subnet 2<o:p></o:p></p>
<p class="MsoNormal"> subnet 10.106.32.0 netmask 255.255.224.0 {<o:p></o:p></p>
<p class="MsoNormal"> range 10.106.32.255 10.106.63.254;<o:p></o:p></p>
<p class="MsoNormal"> option subnet-mask 255.255.224.0;<o:p></o:p></p>
<p class="MsoNormal"> option broadcast-address 10.106.63.255;<o:p></o:p></p>
<p class="MsoNormal"> option routers 10.106.32.1;<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> # Subnet 3<o:p></o:p></p>
<p class="MsoNormal"> subnet 10.106.64.0 netmask 255.255.224.0 {<o:p></o:p></p>
<p class="MsoNormal"> range 10.106.64.255 10.106.95.254;<o:p></o:p></p>
<p class="MsoNormal"> option subnet-mask 255.255.224.0;<o:p></o:p></p>
<p class="MsoNormal"> option broadcast-address 10.106.95.255;<o:p></o:p></p>
<p class="MsoNormal"> option routers 10.106.64.1;<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal">}<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">#Vrf_Default<o:p></o:p></p>
<p class="MsoNormal">group {<o:p></o:p></p>
<p class="MsoNormal"> host modem10 {<o:p></o:p></p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:1b:63;<o:p></o:p></p>
<p class="MsoNormal"> fixed-address 10.106.1.20;<o:p></o:p></p>
<p class="MsoNormal"> filename "basic.bin";<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"> host modem11 {<o:p></o:p></p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:1b:60;<o:p></o:p></p>
<p class="MsoNormal"> fixed-address 10.106.1.21;<o:p></o:p></p>
<p class="MsoNormal"> filename "basic.bin";<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal">}<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">#Vrf_A<o:p></o:p></p>
<p class="MsoNormal">group {<o:p></o:p></p>
<p class="MsoNormal"> host modem20 {<o:p></o:p></p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:1c:8c;<o:p></o:p></p>
<p class="MsoNormal"> fixed-address 10.106.33.20;<o:p></o:p></p>
<p class="MsoNormal"> filename "basic.bin";<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"> host modem21 {<o:p></o:p></p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:1c:ce;<o:p></o:p></p>
<p class="MsoNormal"> fixed-address 10.106.33.21;<o:p></o:p></p>
<p class="MsoNormal"> filename "basic.bin";<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal">}<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">#Vrf_B<o:p></o:p></p>
<p class="MsoNormal">group {<o:p></o:p></p>
<p class="MsoNormal"> host modem30 {<o:p></o:p></p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:20:61;<o:p></o:p></p>
<p class="MsoNormal"> fixed-address 10.106.65.20;<o:p></o:p></p>
<p class="MsoNormal"> filename "basic.bin";<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"> host modem31 {<o:p></o:p></p>
<p class="MsoNormal"> hardware ethernet 00:00:ca:3a:14:8b;<o:p></o:p></p>
<p class="MsoNormal"> fixed-address 10.106.65.21;<o:p></o:p></p>
<p class="MsoNormal"> filename "basic.bin";<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal">}<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">There are two problems we're trying to find a solution to:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></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".<o:p></o:p></p>
<p class="MsoNormal">In the above example, it's from sub-network 10.106.64.0, (for example 10.106.64.254).<o:p></o:p></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.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoListParagraph" style="margin-left:24.75pt;text-indent:-.25in;mso-list:l1 level1 lfo3">
<![if !supportLists]><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Is there a way to specify which sub-network addresses are picked from for dynamic hosts within a shared network space.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></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,<o:p></o:p></p>
<p class="MsoNormal">they get the highest free address from the "highest address shared sub-network".<o:p></o:p></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.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoListParagraph" style="margin-left:24.75pt;text-indent:-.25in;mso-list:l1 level1 lfo3">
<![if !supportLists]><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>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.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks in advance for anyone who may have knowledge in this area,<o:p></o:p></p>
<p class="MsoNormal">G. Turnpaugh<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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