[Dnsmasq-discuss] dnsmasq and RA

Gene Czarcinski gene at czarc.net
Thu Nov 1 16:56:46 GMT 2012


On 11/01/2012 10:08 AM, Simon Kelley wrote:
> On 01/11/12 12:59, Gene Czarcinski wrote:
>> On 10/31/2012 04:41 PM, Gene Czarcinski wrote:
>>> Instead of running both radvd and dnsmasq, I would like to run only
>>> dnsmasq and have it do what is now being done by radvd.
>>>
>>> This is for libvirt so there are some specifics which could help.
>>>
>>> 1. There will be one and only one interface for an instance of dnsmasq.
>>>
>>> 2. Currently (at least with some patches I have created) run one ipv4
>>> dhcp subnetwork or one ipv6 dhcp supnetwork or both one ipv4 network
>>> and one ipv6 network.
>>>
>>> 3.  If a dhcp-range is specified for the ipv6 subnetwork then I need
>>> the AdvManagedFlag on which (I believe) is done with the additional
>>> dsnmasq parameter "enable-ra".
>>>
>>> 4.  But, I may have an IPv6 subnetwork but dhcp-range has not been
>>> specified.  In this case I want the AdvManagedFlag off.  This one is
>>> the situation that I am not clear on.
>>>
>>> 5.  None of the other dnsmasq capabilities with respect to RA will be
>>> used.
>>>
>>> Comments/suggestions?
>>>
>>> If this requires a little enhancement patch, I am willing.
>>>
>>>
>> OK, I believe I have answered my own question but I would still like
>> confirmation.
>>
>> I ran a test with no radvd running ... only dnsmasq.  With enable-ra and
>> dhcp-range specified for ipv6 addresses, the client side gets a dhcp6
>> address and RA default route.
> Check.
>
>>   With enable-ra and NO dhcp-range
>> specified, the client gets a SLAAC address and RA default route.
> That's not what I'd expect. To get RA on a subnet but not dhcp, you need
> to have
>
> dhcp-range=<subnet>,ra-only
>
> enable-ra is superfluous in that case.
Yup!  Now works like a charm.

with real dhcp-range and enable-ra I get dhcp6 and RA route.

with dhcp-range=<ipv6-subnet>,ra-only I get SLAAC address and RA route.

And, in both cases the is an RDNSS entry in /etc/resolve
>> With enable-ra and dhcp-range,I do notice a lot of RTR-ADVERT messages
>> ... like one every couple of seconds.  Is there a way to suppress this
>> message and/or increase the time between the events or at least the
>> messages [that is without disabling dhcp logging] ?
> The frequency will decrease over time. It's roughly every 10 seconds for
> the first minute, and then about every 10 minutes.
>
>
I will need to let it run for a while ... these have been quick tests

Gene



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