DHCP on-the-fly block assignment
Solution 1
Ideally, you'd modify dhcpd to support address assignment based on Option82, equivalent to the "hardware" lines in host objects. I've done it with the OpenBSD dhcpd when I worked at an ISP, which has a simpler internal structure to isc-dhcpd.
If you're not in a position to do that, then look at omapi(3) and omshell(1); you'd use OMAPI to dynamically create "class" and "pool" objects, to implement Zypher's suggestion. I just checked dhcpd.h
and the class
struct has an OMAPI_OBJECT_PREAMBLE
, so this should be possible. Beware that the documentation on OMAPI can be a little ... skimpy.
Solution 2
So i havn't done this with option 82, but your best bet would be to use classing in isc dhcpd.
What you would do is setup a class like:
class "userclass1" {
match if substring(option agent.circuit-id, 2, 2) = "<your_id1>";
}
class "userclass2" {
match if substring(option agent.circuit-id, 2, 2) = "<your_id2>";
}
Then in your pool statement:
pool {
allow members of "userclass1";
range 10.0.0.11 10.0.0.50;
}
pool {
allow members of "userclass2";
range 10.0.0.51 10.0.0.100;
}
Reference: dhcpd.conf
This should at least get you on the right track, i don't have my play server up to test it, but i've done something similar with other options.
Solution 3
Maybe you can start from here:
Never used, but with a bit of scripting I think it could work.
EDIT
man omshell(1) would give some other examples
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Andomar
Updated on September 17, 2022Comments
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Andomar almost 2 years
We have a large number of clients who connect to our DHCP machine. We want to assign some of them to a different IP block, which is routed with lower priority. Every DHCP lease renewal, we'd like to check a database and decide which IP block we'd like to assign a customer to.
Is there a way to have a DHCP server execute a script, look in a database, or execute some dynamic code when deciding which address to assign in which pool? Each client is uniquely identified by option82, aka "DHCP Relay Agent Information Option".
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Admin almost 14 yearsWhich DHCP server on what OS?
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Admin almost 14 yearsThis sounds like a carrier-type setup... is that the case? I would be surprised if something like this already existed in the open tools. I would probably look at writing it myself. Very interesting question though!
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Admin almost 14 years@Zypher: Debian OS, regular dhcpd @MikeyB: Yes, carrier setup
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Andomar almost 14 yearsActually, switching VLAN is what we'd like to avoid. VLAN switches confuse the client's modems and take a long time to execute
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Andomar almost 14 yearsWouldn't we have to reset dhcpd every time there is a change? Is it possible to have pool membership determined dynamically by a script call?
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Zypher almost 14 years@Andomar: Yep you would. Unfortunately i don't think so - but i could be very wrong there