[Dnsmasq-discuss] DHCP leases in multiple VLANs

Simon Kelley simon at thekelleys.org.uk
Tue Aug 31 21:08:10 BST 2010

Ferenc Wagner wrote:
> Hi,
> I came to realise that dnsmasq can't register multiple addresses of a
> single client obtained in different VLANs, because they belong to the
> same MAC address, so knock each other out of the lease file.
> I suggest the lease file contain the interface as well (and the
> interface also passed to the dhcp-script) to overcome this limitation.
> Would this be acceptable?

The interface isn't a good thing to keep the leases unique: it doesn't
deal with requests that go via  DHCP-relay agents, for one thing.

A good workaround would be to set the client-id differently for each
VLAN. DHCP clients should maybe do this anyway: it's dodgy to have the
same MAC address in more than one broadcast domain at the same time.

It may be possible to relax dnsmasq a bit: really only the IP address
needs to be unique in the lease database, but I'm not quite sure there
wouldn't be obscure consequences.



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