[Dnsmasq-discuss] IPv6 constructor option - confused!

Kevin Darbyshire-Bryant kevin at darbyshire-bryant.me.uk
Thu May 2 17:54:06 BST 2013

On 02/05/2013 17:00, Simon Kelley wrote:
> It is how I expected it to work, exactly.
> DHCP-PD client gets prefix, and assigns <prefix>::1 to LAN interface.
> dnsmasq gives addresses between
> <prefix>::2 and <prefix>::<whateveryouwant>
> to clients on the LAN.

Which (contrived case) isn't ideal if for some reason the DHCP-PD client
assigns prefix:FFFF:FFFF:FFFF:FFFF to the lan interface,
'cos the constructor has nowhere to go.  The constructor will go up from
the lowest address, it doesn't appear to work down,
though it does sort the addresses in syslog from lowest to highest.  But
this is VERY contrived :-)

>> So is this an oversight or some tomato based wierdness...either way, how
>> can I help to sort it out?
> Suggest an alternative, given that constructing a DHCP range based on
> any address in a prefix is not desirable.
Hmmmm, what about seeing if the interface in question has an address
inside the DHCP constructed range and if it does then use the prefix? 
Or is that excluded by your above statement?

Perhaps if I explain what I'm trying to do it may help.  I'm trying to
remove the requirement for RADVD in the tomato router
environment.  There are a number of potential benefits, not least having
an equivalent local DNS service to the IPv4 dhcp/dns service (privacy
extensions not helping but)  My thought was that the 'constructor'
option was ideal, in that I could assign a constructor range of ::0
-::FFFF:FFFF:FFFF:FFFF and it would pick up the prefix and start serving
addresses through RA & DHCPv6.  Unfortunately it looks like what I would
like isn't quite what 'constructor' actually gives me.


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