one-lease-per-client... seriously

Chuck Anderson cra at WPI.EDU
Sun Sep 18 07:21:36 UTC 2016

On Fri, Sep 16, 2016 at 08:00:15AM +0100, Simon Hobson wrote:
> On 15 Sep 2016, at 21:00, Brian Rak <brak at> wrote:
> > I'm running into an issue where DHCPD (v4.3.4 and older versions) is issuing multiple leases to the same mac address.  It appears to be looking at the DHCP Client-ID field to determine what a unique client is.
> That is by design as is **REQUIRED** by the RFCs.
> It's a long standing problem that some real-world situations clash with this - most notably when there is multi-boot with Windoze and anything else since Windows defaults to using the MAC address as client-id and everything else defaults to not sending one. But that's what the standards require and the ISC implementation has always been intended to be a "reference" implementation that completely meets the standards as laid down (unlike several other servers which really do break the rules a lot).
> >  I'd much rather it ignore everything except for the client's mac address, but I can't seem to find an option to do this.
> It used to require patches, but I see Jeff has suggested an option to deal with this.

A better way might be to identify the various boot stages and hand out
very short leases for PXE, etc.  That way you don't violate the
standard, but the extra leases don't hang around for very long.

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