[Dnsmasq-discuss] SLAAC is working, but DHCPv6 isn't

Ken Welker benedictcc at yahoo.com
Thu Oct 30 22:54:54 GMT 2014

On 10/24/2014 9:49 AM, Neil Jerram wrote:
>>> Hi Ken,
>>>> Running a packet capture on both my server and a host, I can see the
>>>> "solict" packet from the host to the server; however the server doesn't
>>>> send an "advertise" packet back to the client (but logging in syslog
>>>> says that it *did* send a DHCPADVERTISE, and shows a valid IPv6 address
>>>> that it "offered" the client.)
>>>> No firewall rules prevent this communication; they're wide open for
>>>> internal traffic.
>>>> Would anyone have ideas on why dnsmasq isn't replying to the solicit
>>>> (but saying that it did)?
>>> How sure are you that dnsmasq doesn't send the DHCPADVERTISE?  Have
>>> you already done something else, e.g. running tcpdump, in order to be
>>> sure that that message isn't sent?  Could it be that the message is
>>> sent but for some reason doesn't reach the client?
>>> Regards,
>>> 	Neil
>> Hi Neil,
>> I did say that I was running packet captures on both the server and the
>> host.  If dnsmasq had sent any replies, I would have seen them leaving
>> the server, even if they didn't reach the client for whatever reason.
> I'm sorry.  I don't know how I managed to miss that you'd written that.
>> I'm wondering if there's some complex interaction between the items in
>> my configuration that causes some rare bug to manifest; again, SLAAC
>> works just fine at the same time.  I assume others have it working fine
>> - anything strange about the config I posted?  Surely the order doesn't
>> matter, right?
> I'm afraid I'm stumped.  Your config looks reasonable to me.
> Regards,
> 	Neil

Looks like this is still happening under version 2.72 (which I expected
from the changelog, but still tested to be sure).  The syslog still says
it is sending a DHCPADVERTISE with an IPv6 address in the correct range
to the host, but packet captures on the server as well as the host don't
show anything going out from the server.

I'm still wondering if it's some undocumented interaction between
options; I found an email
which said that the "listen-address" option seems to turn off the
"enable-ra" option, which I had found independently as well.

I can't seem to find any notice of option combinations that silently
turns off dhcpv6 replies.  Would anyone else be able to look into this?


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