[Dnsmasq-discuss] dnsmasq 2.62-3 as DHCPv6-Server and RA-Server: Bug sending router's link-local instead of global address as gateway and DNS-server?

[Simon Kelley]

On 21/01/14 13:02, Martin Babutzka wrote:
> Thanks for the replies! I hesitantly updated to dnsmasq-2.68 since I
> first wanted to stick to the version provided with Debian wheezy. The
> quiet-options really reduce the amount of syslog messages except for:
> "dnsmasq-dhcp[23663]: no address range available for DHCPv6 request via
> eth5"
> Concerning the link-local addresses it actually looks like this is the
> default when advertising gateways in local networks. Unfortunately other
> software to proxy/relay dhcpv6 and ra can not handle it properly. It is
> basically possible to also advertise the routers global address (see
> here: http://www.macfreek.nl/memory/Non-Local_IPv6_Router_Advertisement
> and the RFC here: http://tools.ietf.org/html/rfc6275#section-7.2 ). Is
> this option also available in dnsmasq? In radvd it is called
> "AdvRouterAddr on;".

There are two different thinks here: the router address and the DNS 
server address.

I think that the router address is always taken as the source address of 
the RA packets, and therefore has to be link-local.

The DNS server address is advertised as the global address in DHCPv6 and 
the link-local address in RA, by default.

You can force a particular address in RA and DHCpv6 by using 
dhcp-option, indeed you can specify the option is all zeros to specify 
the global address. This applies to both DHCPv6 and RA so

dhcp-option=option6:dns-server,[::]

will force the dhcpv6 DNS address to be the global address (no change) 
and the RA DNS address to be the same, which is what you want, I think.

The next release adds the ability to specify link-local, ULA or global 
addresses.


Cheers,

Simon.


> Many regards,
> Martin
>> Kevin Darbyshire-Bryant <kevin at darbyshire-bryant.me.uk> hat am 21.
>> Januar 2014 um 12:16 geschrieben:
>>
>> On 21/01/2014 10:40, Martin Babutzka wrote:
>>> Hello,
>>> We are using this great piece of software so far as DNS cacher but
>>> want to implement it also as IPv6 server by now. DHCPv4 is handled by
>>> another software at the moment (isc-dhcp-server) but we think the
>>> dnsmasq 2.62-3 is quite suitable for our need of an DHCPv6- and
>>> RA-server.
>>> I activated the features in dnsmasq.conf which I think should set-up
>>> a working DHCPv6/RA-Server (see compressed config file below). From
>>> then on the server distributed ipv6-addresses from the correct range.
>>> Unfortunately some error occured: As wanted it also distributed
>>> Gateway and DNS-server but it used the LINK-LOCAL v6 address of the
>>> corresponding interface instead of the Global configured address
>>> (2010:7d0:904:1202::1). Is this a bug or misconfiguration?
>>> Another independent question: With this configuration dnsmasq starts
>>> to be pretty noisy in the syslog. Is there any option to reduce the
>>> verbosity once the system works?
>> v2.68 includes 'quiet-dhcp, quiet-dhcp6 & quiet-ra' options which
>> significantly help the syslog noise.
>>
>> I think it's correct behaviour to advertise the link-local address.
>>
>> Hope that helps.
>>
>> Kevin
>
>
>
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