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Do I need Linode's IPv6 nameservers in /etc/resolv.conf?
https://forum.linode.com/viewtopic.php?f=19&t=9420		 Page 1 of 1
Author:  robg [ Sat Sep 29, 2012 10:45 am ]
Post subject:  Do I need Linode's IPv6 nameservers in /etc/resolv.conf?
I'm setting up a new Linode and while I'm not using IPv6 directly at this time, I'd like to configure it to be IPv6-ready. In my "Remote Access" tab, I see the following under "DNS Resolvers":

Code:
97.107.133.4
207.192.69.4
207.192.69.5
2600:3c03::2
2600:3c03::3


However, I only see the IPv4 addresses above in /etc/resolv.conf and no mention of the IPv6 ones. The Linode documentation doesn't seem to mention this at all, either. IPv6 seems to be set up though and I can ping ipv6.google.com just fine.
Author:  hoopycat [ Sat Sep 29, 2012 11:27 am ]
Post subject:  Re: Do I need Linode's IPv6 nameservers in /etc/resolv.conf?
You don't need them as a necessary condition of using IPv6. IPv6 is just a transport layer for DNS, and whether or not you use IPv6 to query DNS will not impact the results of the query(*).

The reason the IPv6 resolvers don't appear there is because DHCPv4 is used to populate /etc/resolv.conf automatically, and it doesn't know about the IPv6 resolvers. You are more than welcome to disable DHCP and use a static network configuration, which will let you do whatever you want with /etc/resolv.conf.

(*) For pedants: We'll assume all the DNS servers involved neglect the source IP address of the query when deciding which records to return. That's true in this case.
Author:  robg [ Sat Sep 29, 2012 11:53 am ]
Post subject:  Re: Do I need Linode's IPv6 nameservers in /etc/resolv.conf?
hoopycat wrote:
You don't need them as a necessary condition of using IPv6. IPv6 is just a transport layer for DNS, and whether or not you use IPv6 to query DNS will not impact the results of the query(*).

The reason the IPv6 resolvers don't appear there is because DHCPv4 is used to populate /etc/resolv.conf automatically, and it doesn't know about the IPv6 resolvers. You are more than welcome to disable DHCP and use a static network configuration, which will let you do whatever you want with /etc/resolv.conf.

(*) For pedants: We'll assume all the DNS servers involved neglect the source IP address of the query when deciding which records to return. That's true in this case.


Thanks for the help! I'm using static networking actually. While we're on the subject, can you tell me if my /etc/network/interfaces file looks correct? I'm running Debian 6. I added in IPv6 support, but I'm not sure if I did it correctly.

Code:
# localhost 

auto lo
iface lo inet loopback

# eth0 interface 

auto eth0 eth0:0

# public

iface eth0 inet static
   address   [Linode IPv4 IP]
   netmask   255.255.255.0
   gateway   [Linode IPv4 Gateway IP]

# private

iface eth0:0 inet static
   address   [Linode IPv4 Private IP]
   netmask   255.255.128.0

# IPv6

iface eth0 inet6 static
   pre-up   modprobe ipv6
   address  [Linode IPv6 IP]
   up       echo 0 > /proc/sys/net/ipv6/conf/all/autoconf
   netmask  64
   gateway  fe80::1


After restarting, I noticed /proc/sys/net/ipv6/conf/all/autoconf was still set to 1 instead of 0. `ping6 fe80::1` also doesn't seem to work? But I'm able to `ping6 ipv6.google.com` just fine. Here's the output of `ip -6 address show eth0`:

Code:
3: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 [Linode IPv6 IP]/64 scope global dynamic 
       valid_lft 43199sec preferred_lft 43199sec
    inet6 [Linode IPv6 Link-Local IP]/64 scope link 
       valid_lft forever preferred_lft forever
Author:  hoopycat [ Sat Sep 29, 2012 12:50 pm ]
Post subject:  Re: Do I need Linode's IPv6 nameservers in /etc/resolv.conf?
My network config looks something like:

Code:
auto eth0
iface eth0 inet static
    address 97.107.134.213
    netmask 255.255.255.0
    gateway 97.107.134.1
    up /sbin/ip addr add 2600:3c03::f03c:91ff:fe96:1dc9 dev eth0 # main
    up /sbin/ip -6 route add default via fe80::1 dev eth0
    up /sbin/ip addr add 2600:3c03::13:3025/64 dev eth0 preferred_lft 0 # mail.sodtech.net
    up /sbin/ip addr add 2600:3c03::13:3123/64 dev eth0 preferred_lft 0 # ntp.sodtech.net
    up /sbin/ip addr add 2600:3c03::13:3142/64 dev eth0 preferred_lft 0 # xn--1xa.hoopycat.com
    up /sbin/ip addr add 2600:3c03::13:3700/64 dev eth0 preferred_lft 0 # mo.lestor.net
    # ....


I don't turn off autoconf or do anything particularly unusual. If it works, it works. -rt
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