[Dnsmasq-discuss] Announce: dnsmasq-2.66
Simon Kelley
simon at thekelleys.org.uk
Thu Apr 18 09:41:40 BST 2013
On 17/04/13 16:56, Jim Bos wrote:
> On 04/17/2013 03:08 PM, Simon Kelley wrote:
>> Add "constructed DHCP ranges" for DHCPv6. This is intended
>> for IPv6 routers which get prefixes dynamically via prefix
>> delegation. With suitable configuration, stateful DHCPv6
>> and RA can happen automatically as prefixes are delegated
>> and then deprecated, without having to re-write the
>> dnsmasq configuration file or restart the daemon. Thanks to
>> Steven Barth for extensive testing and development work on
>> this idea.
>
> Simon,
>
> Excited about this new feature as I now have a hardcoded prefix (which
> fortunately my ISP doesn't change very often).
>
> However, either I'm doing something wrong or there is something not working:
>
> I changed
> dhcp-range=2001:XXX:YYYY:ZZ::, ra-stateless, ra-names
> enable-ra
>
> to
>
> dhcp-range=::,constructor:eth0, ra-stateless, ra-names
> enable-ra
>
> And in the log I see this:
>
> Apr 17 17:11:24 dnsmasq[8972]: compile time options: IPv6 GNU-getopt
> no-DBus i18n IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth
>
> Apr 17 17:11:24 dnsmasq-dhcp[8972]: DHCPv6 stateless on ::, template for
> eth0
> Apr 17 17:11:24 dnsmasq-dhcp[8972]: DHCPv4-derived IPv6 names on ::,
> template for eth0
> Apr 17 17:11:24 dnsmasq-dhcp[8972]: router advertisement on ::, template
> for eth0
> Apr 17 17:11:24 dnsmasq-dhcp[8972]: IPv6 router advertisement enabled
>
> However, NO RA's are being sent on eth0 :-(
>
>
> For reference, changing back the line I get
>
> Apr 17 17:34:25 dnsmasq[9198]: compile time options: IPv6 GNU-getopt
> no-DBus i18n IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth
>
> Apr 17 17:34:25 dnsmasq-dhcp[9198]: DHCPv6 stateless on 2001:XXXX:YYYY:ZZ::
> Apr 17 17:34:25 dnsmasq-dhcp[9198]: DHCPv4-derived IPv6 names on
> 2001:XXXX:YYYY:ZZ::
> Apr 17 17:34:25 dnsmasq-dhcp[9198]: router advertisement on
> 2001:XXXX:YYYY:ZZ::
> Apr 17 17:34:25 dnsmasq-dhcp[9198]: IPv6 router advertisement enabled
>
> Apr 17 17:34:39 dnsmasq-dhcp[9198]: RTR-ADVERT(eth0) 2001:XXXX:YYYY:ZZ::
> Apr 17 17:34:45 dnsmasq-dhcp[9198]: RTR-ADVERT(eth0) 2001:XXXX:YYYY:ZZ::
>
>
> Jim
>
>
You need the host-identifier part of the address in the dhcp-range to
match the host identifier part of the address on the local interface. So
if your prefix is 2001:XXX:YYYY:ZZ:: and the address of eth0 is
consequently set to, say
2001:XXX:YYYY:ZZ::1
then you need a dhcp-range statement of
dhcp-range=::1 ,constructor:eth0, ra-stateless, ra-names
The reason for this is that once advertisements are being sent for
2001:XXX:YYYY:ZZ:: then eth0 can easily end up with SLAAC address on
that prefix as well as its hard-coded one. If any address in the prefix
was ok to trigger RAs, then you could never get rid of a prefix simply
deleting the original address from the interface.
Cheers,
Simon.
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