[Dnsmasq-discuss] Different IP address for a single MAC address

Simon Kelley simon at thekelleys.org.uk
Thu Apr 11 14:17:56 BST 2013

On 11/04/13 13:16, Tsachi wrote:
> Hey,
> I am working with ver 2.61
> I came across a dnsmasq.leases file which consists of the following 3 lines:
> 605245 10:0b:a9:ad:bc:58 pc
> 01:52:41:53:20:10:0b:a9:ad:bc:58:00:00:00:00:00:00
> 605245 10:0b:a9:ad:bc:58 *
> 01:52:41:53:20:10:0b:a9:ad:bc:58:00:00:01:00:00:00
> 605231 10:0b:a9:ad:bc:58 * 01:10:0b:a9:ad:bc:58
> This indicate that the same MAC (different Client-ID) received 3 different
> IP address
> I don't have an access to the HOST computer (WIFI), and I was not able to
> capture the DHCP packets, but the logs shows that
> they were sent at around the same time (seconds difference).
> Any idea how-come an host sends 3 different Client IDs ?

Possibly three different DHCP clients running at the same time. It looks 
like two of them have DUID client-ids, and one is using the traditional 
MAC-address based client-id.
> Is it suppose to be that dnsmasq gives different IPs to the same MAC ?

Yes, if the client-id is provided, that gets used to identify the 
client, and not the MAC address. So three different client-ids gives 
three leases and three addresses.

You can change this behaviour for individual hosts with something like

dhcp-host=10:0b:a9:ad:bc:58, id:*

but that's not what the standard says.



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