[Dnsmasq-discuss] DHCP errors with vlans and multiple subnets

David Joslin davidj at nkcc.org.uk
Mon Mar 3 13:20:18 UTC 2014

I have dnsmasq (version 2.69test8-78-g6e0290a) on a router running the
tomato firmware (and I hope it's OK to post questions about such a router
here). My network is split into several vlans, each with its own subnet,
and one of the vlans has several wi-fi access points which obtain their IP
addresses from the router using DHCP. The access points all have entries in
the dhcp-hosts file reserving certain IP addresses for them. Up till
recently everything was working fine - the access points always picked up
the correct addresses.

However, something weird is now happening. When the access points now
request addresses, dnsmasq is offering addresses from the other subnets and
isn't offering the addresses reserved in dhcp-hosts. Dnsmasq then logs an
error saying that the offered address conflicts with the address recorded
in the hosts file.

The messages from the log are shown below.

I've checked over and over again and I can't find anything that's changed
in the configuration of the network or router and I can't work out what's
causing this.

Any help would be gratefully received.



DHCPDISCOVER(br0) dc:9f:db:e8:98:b8
DHCPOFFER(br0) dc:9f:db:e8:98:b8
DHCPDISCOVER(br1) dc:9f:db:e8:98:b8
DHCPOFFER(br1) dc:9f:db:e8:98:b8
DHCPDISCOVER(br2) dc:9f:db:e8:98:b8
DHCPOFFER(br2) dc:9f:db:e8:98:b8
DHCPREQUEST(br0) dc:9f:db:e8:98:b8
DHCPACK(br0) dc:9f:db:e8:98:b8 Room4UAP
not giving name Room4UAP to the DHCP lease of because the name
exists in /etc/dnsmasq/hosts/hosts with address
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