[Dnsmasq-discuss] local.net / ipv6 confusion

Ken Bass kbass at kenbass.com
Tue Oct 22 19:39:51 BST 2013


Hello,

My dnsmasq.conf file contains (running on my asus (merlin) router - 
using dnsmasq 2.65):
domain=local.net
local=/local.net/
and
dhcp-option=lan,option:domain-search,local.net

Everything was working fine. I use server1.local.net as a FQDN 
throughout my local network.

And then yesterday I enabled ipv6 on my router and this all stopped 
working (or maybe only on windows machines). So I am wondering if I 
could get some help on how to fix this.
My suspicion is that the resolver on Windows machines is perhaps 
ignoring my local DNS server and instead querying an actual ipv6 server 
from the ISP so it never finds my host.local.net names.

I did verify via some test websites that the router is working with 
native ipv6.
The router is currently running radvd, dhcp6c, and dhcp6s.

So i think the solution to this is for dnsmasq to at least handle dns 
queries locally and forward them.

1) Do I need radvd or is 'enable-ra' equivalent? I noticed in my 
/etc/radvd.conf file that 'AdvLinkMTU 1480'. I dont see how dnsmasq does 
an equivalent thing and whether this is even important.
2) I've changed the RDNS in the /etc/radvd.conf and replaced it with the 
ipv6 of my router.
3) On windows 7, is there something I need to do to force a refresh of 
these ipv6 dns servers? They don't seem to change even with ipconfig 
/release and /renew. However after rebooting my router and waiting 10-15 
minutes, it seemed to update.
4) I am thinking that for dnsmasq to handle the ipv6 queries, it needs 
to bind on the ipv6 address and that can only occur if I add a 
dhcp-range (which means killing dhcp6s)?

   I added the following
   dhcp-range=lan6,XXXX:XXXX:XXXX:XXXX::, ra-stateless, ra-names
   dhcp-option=lan6,option:domain-search,local.net
#ISP ipv6 DNS
   server=2001:558:feed::1
   server=2001:558:feed::2

Am I on the right track? Currently it seems to work (still using radvd), 
though I'm not sure if it is my imagination, but latency to websites 
seem longer. Are added DNS lookups causing this?

This appears to be working which raises other questions (perhaps more 
ipv6 related).
- When I look some of my existing Linux machine with ifconfig, I notice 
that they have an ipv6 global address which contains the correct prefix. 
Where did this come from? I am unaware that those machine are running 
any dhcpv6 client. I did nothing to them, yet they can ping6 the router 
and ipv6.google.com. Does the ip stack handle processing router 
advertisements itself? How does it know?
- How do I assign meaningful ipv6 DNS names to these when they are using 
this stateless configuration? Or do I need to use stateful?
- Now that I've got this wonderful /64 address space, if I want to 
access these machines from the internet do I need to do anything special?



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