[Dnsmasq-discuss] IPv6 constructor option - confused!

Kevin Darbyshire-Bryant kevin at darbyshire-bryant.me.uk
Wed May 1 16:26:21 BST 2013

Hi Simon,

I find myself confused by the use of the constructor option for building
DHCPv6 address ranges.

edited dnsmasq.conf file:

dhcp-range=tag:br0,::1, ::FFFF, constructor:br0, ra-names, 12h

Now on my Tomato based router this picks up then (tunnelled) ipv6 LAN
address on the BR0 interface, which happens to be ISP_PREFIX::1  It
builds a range ISP_PREFIX::1 -> ISP_PREFIX::FFFF and all is well.

However, others do not have a nice neat '::1' they have (presumably
because it's been delegated to them by their ISP) something like
ISP_PREFIX::DEAD:BEEF:F00D.   Now there are two problems as I see it
with this:

1) I now need to specify my starting IP address range as DEAD:BEEF:F00D
otherwise dnsmasq doesn't find the prefix and doesn't serve an IPv6
addresses at all.  In which case why am I even bothering to tell it the
interface in the constructor?

2) The range parameter (:FFFF) implies I can define a range from
DEAD:BEEF:F00D to DEAD:BEEF:FFFF only with nothing lower than F00D.

I'm sure I'm being stupid here, please educate me.... again :-)


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