[Dnsmasq-discuss] ignoring unknown devices ..

[Simon Kelley]

Ben wrote:
> Simon Kelley wrote:
> 
>>Ben wrote:
>>  
>>
>>>I need to setup dnsmasq to ignore unknown devices and I have been able
>>>to do so with 2.40 but I have a configuration issue that I think may be
>>>a bug.
>>>
>>>Here is what i want to have.
>>>
>>>   dhcp-range=10.7.5.100,10.7.5.254,24h
>>>   dhcp-ignore=#known
>>>   dhcp-hostsfile=/etc/dnsmasq.d/#hostsfile#
>>>
>>>   dhcp-host=tc01,10.7.5.13
>>>   dhcp-host=tc02,10.7.5.14
>>>
>>>This should, in theory, allocate IPs to devices with  MAC addresses
>>>listed in the '#hostsfile#' and devices named 'tc01' and 'tc02'.  But
>>>when "dhcp-ignore=#known" is defined 'tc01' and 'tc02' are ignored.
>>>
>>>This config works, but requires the MAC for 'tc01' to be defined.
>>>
>>>   dhcp-range=10.7.5.100,10.7.5.254,24h
>>>   dhcp-ignore=#known
>>>   dhcp-hostsfile=/etc/dnsmasq.d/#hostsfile#
>>>
>>>   dhcp-host=00:20:4a:9c:52:c2,10.7.5.13,tc01
>>>
>>>So what i am looking for is to be able to use "#known" and "hostsfile"
>>>as well as allocate fixed IPs to devices by name.
>>>
>>>Is this by design or a bug?
>>>    
>>
>>It's difficult to classify it as either: it's just a limitation.
>>
>>If you have a line in /etc/dnsmasq.d/#hostsfile# with am MAC address,
>>that's precisely equivalent to putting
>>
>>dhcp-host=<MAC address>
>>
>>in /etc/dnsmasq.conf.
>>
>>That doesn't do what you want because the information about a host is
>>spread over more than one dhcp-host directive. For each DHCP
>>transaction, dnsmasq searches for exactly one dhcp-host directive (it
>>searches by client-id, then by MAC address and finally by hostname)
>>
>>In your case it will find the MAC address but then stops searching and
>>never finds the IP address and hostname.
>>
>>
>>Putting everything into one line works, as you found out, another
>>possibility is to put (MAC address, IP address) or (MAC address,
>>hostname) pairs in /etc/ethers. These are matched against (and combined
>>with) dhcp-host lines.
>>  
> 
> 
> Thanks for the reply Simon, it is appreciated.
> 
> The MAC of the host, 'tc01',  that requires a static is not put into the 
> '#hostsfile#', but i have tried it both ways.  The only entry that 
> should match is the "dhcp-host=tc01,10.7.5.13" in the main config file.
> 
> So the order "client-id, then by MAC address and finally by hostname" 
> should be honored, right? 

Right. But be sure that the host is actually sending its name in the 
DHCP messages. Many clients (especially Unix clients) don't, unless 
specially configured.


Cheers,

Simon.

> 
> I will re-test because it has been a while.
> 
> Ben
> 
>