[Dnsmasq-discuss] Need a little IPv6 clarification

Gene Czarcinski gene at czarc.net
Sat Sep 15 16:11:56 BST 2012


On 09/15/2012 10:34 AM, Gui Iribarren wrote:
> On Sat, Sep 15, 2012 at 11:20 AM, Gene Czarcinski <gene at czarc.net> wrote:
>> On 09/14/2012 03:39 PM, Gene Czarcinski wrote:
>>> I have been trying to get some (virtual) IPv6 networks working with
>>> dnsmasq acting as both an dhcp6 server and a dns server.  I really do not
>>> care how the IP6 addresses are assigned but I do want the system names in
>>> dnsmasq's dns service so that these systems can be referred to by name.
>>>
>>> At some point in time I had dnsmasq actually handing out IP6 addresses via
>>> dhcp ... or it certainly looked like that since the address was in the range
>>> I specified.  That said, I no longer know just what my configuration was.
>>>
>>> Basically, I am not sure I understand the meanings or effects of the
>>> various parameters on the dhcp-range specification. Specifically, what
>>> specifying nothing or ra-name or slaac or ra-stateless or ra-only means ..
>>> what are the effects of each are ... or when you combine them what happens.
>>>
>>> I have read the dnsmasq man page but I need a little more info. It sure
>>> would be nice to see what a working configuration looked like.
>>>
>>> It would be nice if dnsmasq's dns service could be updated regardless of
>>> how the address is specified (other than manually) but if only a subset (or
>>> even one) will work ... well, that works for me too.
>>>
>>> Yes, I searched this mailing list and found the messages saying that you
>>> had to specify the fqdn and not just the hostname ... but that was well
>>> after I did a lot of parameter "testing".
>>>
>>> My next step is to take a look at the dnsmasq code to see if I can figure
>>> things out but a few pointers and hints would be appreciated.
>>>
>> OK, progress.  I have gotten dnsmasq to do the right thing (I belieive) for
>> IPv6 addresses.  However, dns is not updating.  I believe the reason for
>> that is that NetworkManager is not sending the FQDN with the dhcp6 request.
>>
>> But I still have a question.  Reading the man file for dnsmasq I see that
>> specifying "ra-names" that dnsmasq should go through this dance to do a dns
>> update.  What needs to be specified to get that?
> root at host:~# tail -n2 /etc/dnsmasq.conf
> enable-ra
> dhcp-range=lan, 2001:db8::, ra-names
>
> do note that the ipv6 won't appear in the leases file, but yields
>
> Sep 15 11:19:48 dnsmasq-dhcp[2003]: DHCPREQUEST(br-lan) 10.254.1.56
> de:ad:be:ca:fe:ca
> Sep 15 11:19:48 dnsmasq-dhcp[2003]: DHCPACK(br-lan) 10.254.1.56
> de:ad:be:ca:fe:ca cubito
> Sep 15 11:19:48 dnsmasq-dhcp[2003]: RTR-ADVERT(br-lan) 2001:db8::
> Sep 15 11:19:48 dnsmasq-dhcp[2003]: SLAAC-CONFIRM(br-lan)
> 2001:db8:dead:beff:feca:feca cubito
>
> and
>
> root at colmena-gw:~# nslookup cubito
> Server:    127.0.0.1
> Address 1: 127.0.0.1 localhost
>
> Name:      cubito
> Address 1: 2001:db8:dead:beff:feca:feca cubito.domain.net
> Address 2: 10.254.1.56 cubito.domain.net
>
>
Thank you.

That worked as far as getting an IP6 address and updating dnsmasq's dns 
db.  This demonstrates that what I believed (that dnsmasq was working 
properly) is true.  Unfortunately, this is not really dhcp6 and it is 
not stateful.  But, to do that (at least on Fedora) I will need to get 
NetworkManager fix so that it sends the fqdn for ipv6 dhcp.

Gene



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