Clarification on fixed-address statement

Sten Carlsen stenc at
Fri Apr 29 20:50:34 UTC 2011

You do keep the fixed addresses in a different range than the dynamic?

A fixed address statement does not prevent the same address being handed
out as dynamic if it lies within that range.

On 29/04/11 22:06, Jack Kielsmeier wrote:
> Hello,
> We are running ISC DHCP 3.1.0 in a failover configuration. I do know
> that 3.1.0 is a somewhat old version, but it has worked well for us.
> I am wondering if this is the expected behavior of fixed-address
> statements:
> Upon initial inspection, it seems that if you declare a fixed-address
> for a MAC address, that IP address is reserved and can only be used by
> the declared MAC address.
> In reality, we are seeing the DHCP server hand out fixed-addresses to
> any MAC. When the MAC address that is assigned the fixed-address asks for
> an IP, DHCP will attempt to give it the fixed-address if it is free, but
> will hand out another IP if it's unavailable.
> Is this how fixed-address statements are supposed to work? If so, is
> there a way to make sure only a specific MAC address can use a specific
> IP address?
> For reference, this is how we are declaring fixed-addresses:
> host HOSTX { hardware ethernet xx:xx:xx:xx:xx:xx;fixed-address
> ###.###.###.###; }
> I have stripped the MAC and IP address out.
> Thank You,

Best regards

Sten Carlsen

No improvements come from shouting:


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