One DHCP server, two VLANs?
dhcp1 at thehobsons.co.uk
Tue Jan 12 21:04:21 UTC 2016
Karl Denninger <karl at denninger.net> wrote:
> This seems like it should be possible without a lot of hand-wringing, but I can't find the magic smoke recipe for it.... :-)
It is simple - you're just over thinking it !
> Topology is ...
> The DHCP server is on both VLANs via virtual interfaces (FreeBSD) with the port on the switch being told to send both through; it sees and handles traffic from both VLANs just fine.
> But.... I cannot start two instances of dhcpd (one on each sub-interface.) Nor can I find a way to tell dhcpd to read requests from both.
You just start one instance, but in that instance you define both subnets. So say your subnets are 192.168.1.0/24 and 192.168.2.0/24, then you need a config file a bit like this :
subnet 192.168.1.0 ...
subnet 192.168.2.0 ...
Then make sure that it listens on both interfaces. The default is to listen on all broadcast capable interfaces, but distribution specific startup scripts may read settings from a file and limit that.
In operation, the daemon tracks the packets and the interface they arrive through - from this is knows which subnet any request is for, and the rest happens automagically.
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