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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">You could easily enough do this with a funky “netmask” (the mask that picks out the “even Internet” from the “odd Internet” used to be a favorite puzzler question
of mine) but ISC DHCP, like much other software these past 30 years, may not support that.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> dhcp-users <dhcp-users-bounces@lists.isc.org>
<b>On Behalf Of </b>Stephen Donovan<br>
<b>Sent:</b> Wednesday, January 6, 2021 12:54 PM<br>
<b>To:</b> dhcp-users@lists.isc.org<br>
<b>Subject:</b> Assign IP based on if giaddr is even or odd<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hello Gurus<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I am trying to deploy a series of routers that can use DHCP to provide an IP address to the neighbouring router and once the router is reachable management software will push configuration to it.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">All links between the routers are /31 subnets and it is possible that each router could be configured in each direction, for example if router A is up, then it will offer an address to router B, however if router B is up before A then B
will offer an address to A.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I tried the sample subnet shown below and everything works, if I use the full giaddr in the match statement, however if I try to simplify it to match the class if the giaddr is even or odd doesn't work. My attempt on using a regex to match
even/odd is commented out.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Does anyone have any suggestions on how I could use a different match to hand out different addresses based on if the giaddr is even or odd? Did I make a fundamental mistake in my match statement. I'm willing to use the full match, but
would like to simplify if possible.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thanks in advance<o:p></o:p></p>
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<p class="MsoNormal">Steve<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">#test subnet<o:p></o:p></p>
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<p class="MsoNormal">subnet 11.12.13.44 netmask 255.255.255.254 {<o:p></o:p></p>
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<p class="MsoNormal">log(debug, concat ("giaddr: ", binary-to-ascii(10,8, ".", packet(27,1)))) ;<o:p></o:p></p>
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<p class="MsoNormal">class "cw" {<o:p></o:p></p>
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<p class="MsoNormal">#match if (binary-to-ascii(10,8, ".", packet(27,1)) ~~<o:p></o:p></p>
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<p class="MsoNormal">#"^\d*[02468]$");<o:p></o:p></p>
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<p class="MsoNormal">match if (binary-to-ascii(10,8, ".", packet(24,4)) =<o:p></o:p></p>
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<p class="MsoNormal">"11.12.13.44");<o:p></o:p></p>
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<p class="MsoNormal">}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">pool<o:p></o:p></p>
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<p class="MsoNormal">{<o:p></o:p></p>
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<p class="MsoNormal">allow members of "cw";<o:p></o:p></p>
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<p class="MsoNormal">range 11.12.13.45 11.12.13.45;<o:p></o:p></p>
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<p class="MsoNormal">option routers 11.12.13.44;<o:p></o:p></p>
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<p class="MsoNormal">option subnet-mask 255.255.255.254;<o:p></o:p></p>
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<p class="MsoNormal">}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">pool<o:p></o:p></p>
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<p class="MsoNormal">{<o:p></o:p></p>
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<p class="MsoNormal">deny members of "cw";<o:p></o:p></p>
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<p class="MsoNormal">range 11.12.13.44 11.12.13.44;<o:p></o:p></p>
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<p class="MsoNormal">option routers 11.12.13.45;<o:p></o:p></p>
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<p class="MsoNormal">option subnet-mask 255.255.255.254;<o:p></o:p></p>
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<p class="MsoNormal">}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">}<o:p></o:p></p>
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