[Dnsmasq-discuss] IPV6 RA configuration

Simon Kelley simon at thekelleys.org.uk
Sat Dec 29 20:46:10 GMT 2012


On 29/12/12 13:37, kim-dnsmasq at bluemoose.org.uk wrote:
> Back again – further digging, I think I’ve got it going with RA’s from
> the router (M bit set off, O bit set on which makes sense) and the
> wide-dhcp6 (dhcp6s) dhcp server on Debian – with single line config that
> seems to work.
>
> So I’m just misunderstanding how to setup a DHCPV6 only dnsmasq, without
> it making RA’s.?

I'm catching up with the longer questions below, but this one is easy:

If you don't supply

enable-ra

or mention ra in any dhcp-range, than dnsmasq will not supply RA. 
Dnsmasq always logs when it send an RA, so verifying this should be 
fairly easy.

Cheers,

Simon.

>
> *From:*dnsmasq-discuss-bounces at lists.thekelleys.org.uk
> [mailto:dnsmasq-discuss-bounces at lists.thekelleys.org.uk] *On Behalf Of
> *kim-dnsmasq at bluemoose.org.uk
> *Sent:* 29 December 2012 10:01
> *To:* dnsmasq-discuss at lists.thekelleys.org.uk
> *Subject:* [Dnsmasq-discuss] IPV6 RA configuration
>
> Hi,
>
> This may be a simple lack of comprehension on my part (I’m convinced
> IPV6 will be easier for those who never new V4… J) but can someone
> please point me in the right direction…
>
> I think I’m trying to configure dnsmasq to send a router advertisement
> pointing to a different system (ie not itself).  I can’t see a way to do
> that – which may mean it’s a bad idea!
>
> Background – I’ve got a Billion DSL router and a Debian box – the
> Billion has native IPV4 and V6 to the world (thank you A&A), internally
> it actually runs dnsmasq I believe, but it’s not trivial to get a shell
> so I’ve left that alone.    The Debian box is running anyway so I use
> that as an internal DNS with dnsmasq (just updated to 2.65 from the sid
> deb packages, although I’m still on squeeze) , and as a NAT gateway for
> all the sorts of things which are popping up with RJ45’s on these days I
> don’t want to give public V4’s.
>
> IPV4 – fine – dnsmasq on Debian handles DHCP for the NAT range, and
> happily hands out details telling those things to use the debian box as
> a gateway.  Via MAC based tags, a few others get given a fixed IP and
> default gateway straight to the Billion router – all well.
>
> Initially the Billion came setup for V6 -running both router
> advertisements and DHCPV6 – which would be fine, but of course it sets
> IPV6 DNS to only the external ISP servers, so any internal only hosts
> (printers etc) aren’t listed.  So if a host does DNS over V4 it can see
> all the printers etc, if it uses V6 it only sees the public DNS.   Now I
> know I could go and set up every single device in the A&A public DNS,
> and that would fix it but that feels silly – all I want is to have the
> IPV6 config point to the internal Debian dnsmasq and all will be fine.
>
> The billion seems to run dnsmasq, radvd and dhcp6s, but I can’t easily
> get shell access to edit to the config files directly, so I ‘ve turned
> them off in the web interface and I’m trying to advertise the right
> config from dnsmasq on the debian box.
>
> I’m happy using V6 autoconfig addresses (seems half the point of V6 for
> clients) but I think I need to send router advertisments pointing the
> default gateway directly to the Billion router, not to the Debian box
> where dnsmasq is running (no reason to send the packets via Debian as no
> NAT involved in V6).   I then need to use DHCPV6 to set the DNS server
> to the debian box and all will be well.
>
> I can’t find a way to specify the default gateway sent in the RA from
> dnsmasq – entirely logically it sends its own address and only that.
>
> I tried to get clever and turn RA’s back on from the Billion router and
> disable them on dnsmasq – leaving DHCPV6 on Debian to set DNS and
> turning it off on the router – it sort of works but only some of the
> time which makes me think I’ve missed the point.
>
> Any thoughts? – are RA’s inherently only ever set to the router they are
> sent from?   What’s the best way to set up a network with the DNS on one
> box and the router on another.
>
> Thanks in advance – sorry this is such a long mail!
>
> Cheers
>
> Kim
>
>
>
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