[Dnsmasq-discuss] no-dhcp-interface documentation

Simon Kelley simon at thekelleys.org.uk
Tue Sep 14 20:19:46 BST 2010

Ferenc Wagner wrote:
> Simon Kelley <simon at thekelleys.org.uk> writes:
>> Ferenc Wagner wrote:
>>> Now I firewalled the DHCP traffic coming from the segment I want to
>>> provide only TFTP on to suppress the "no address range available for
>>> DHCP request" messages.  Is there a better way to achieve this?
>> dhcp-range=set:no-dhcp-here,,
>> dhcp-ignore=tag:no-dhcp-here
>> should work, I think.
> It didn't really work out.  I inserted
> dhcp-range=set:no-dhcp-here,,
> dhcp-ignore=tag:no-dhcp-here
> into my config and dnsmasq started to hand out leases:
> dnsmasq-dhcp: DHCPDISCOVER(szie-aotk) 00:21:91:56:dc:83 
> dnsmasq-dhcp: DHCPOFFER(szie-aotk) 00:21:91:56:dc:83 
> dnsmasq-dhcp: DHCPINFORM(szie-aotk) 00:17:a4:43:a5:e1 
> dnsmasq-dhcp: DHCPACK(szie-aotk) 00:17:a4:43:a5:e1 LAB01PC09
> dnsmasq-dhcp: DHCPREQUEST(szie-aotk) 00:21:91:56:dc:83 
> dnsmasq-dhcp: DHCPACK(szie-aotk) 00:21:91:56:dc:83 dlink-56DC83
> dnsmasq-dhcp: DHCPINFORM(szie-aotk) 00:16:76:4c:75:53 
> dnsmasq-dhcp: DHCPACK(szie-aotk) 00:16:76:4c:75:53 zskiss
> dnsmasq-dhcp: DHCPREQUEST(szie-aotk) 00:0f:fe:85:ff:5f 
> dnsmasq-dhcp: DHCPACK(szie-aotk) 00:0f:fe:85:ff:5f csapo
> dnsmasq-dhcp: DHCPREQUEST(szie-aotk) 00:0f:fe:85:ff:5f 
> dnsmasq-dhcp: DHCPACK(szie-aotk) 00:0f:fe:85:ff:5f csapo
> However, isn't the interface name always present as a tag?  I mean, the
> above range corresponds to
> interface=szie-aotk
> in my config (and in the reality), so something like
> dhcp-ignore=tag:szie-aotk
> could possibly work instead?  I didn't find the documentation about the
> implicit tagging by the interface name, maybe I only dreamt it?

You didn't dream it. From the NOTES section of the man page:

"The tag system works as follows: For each DHCP request, dnsmasq
collects a set of valid tags from active configuration lines which
include set:<tag>, including one from the dhcp-range used to allocate
the address, one from any matching dhcp-host (and "known" if a dhcp-host
matches) The tag "bootp" is set for BOOTP requests, and  a  tag whose
name is the name of the interface on which the request arrived is also set."

log-dhcp shows the set of tags set for each DHCP transaction, which
might be useful for checking.



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