[conspire] missing rDNS for (intentionally missing) IPv6

[Tim Utschig]

On Wed, Mar 03, 2021 at 01:41:28PM -0800, Rick Moen wrote:
> what guarantee is there that it would be the same IPv6 address if the
> server got one again?  Or, to reframe the question, how do I make sure
> the autoconfigured IPv6 assignment is deterministic?

I don't know how Comcast does IPv6 these days, but with AT&T I
had a look at the web UI on my Uverse router and noticed an IP
address for a 6RD server*.

  * I would be very surprised if this was actually implemented
    with traditional "servers" and not just a part of their
    router configs - it's certainly been reliable and low-latency
    enough to probably be a core feature of their network.

Knowing a teeny bit about 6RD I thought, "Hmm, I wonder if I can
just plug in one of my AT&T-assigned static IPv4 address and have
a static /60..." Sure enough, it worked perfectly and still does
~5 years later.

I intend to (someday) investigate whether static *native* IPv6 is
something AT&T offers these days. I'm pretty sure they have
native *dynamically-assigned* IPv6 addressing, but that's not
what I want.

Some details of my config (OpenWRT) are below in case it helps:

# /etc/config/network
config interface 'lan'
  option ifname     'eth0.1'
  option type       'bridge'
  option proto      'static'
  option ipaddr     '<internal_ip_of_my_router>'
  option netmask    '255.255.255.0'
  list   dns        '8.8.8.8'
  list   dns        '8.8.4.4'
  list   dns        '2001:4860:4860::8888'
  list   dns        '2001:4860:4860::8844'
  option ip6assign  60

config interface 'wan'
  option ifname     'eth0.2'
  option proto      'static'
  list   ipaddr     '107.209.154.41'
  list   ipaddr     '107.209.154.42'
  list   ipaddr     '107.209.154.43'
  list   ipaddr     '107.209.154.44'
  list   ipaddr     '107.209.154.45'
  # AT&T 6rd prefix + 107.209.154.41
  list   ip6addr    '2602:306:bd19:a290::1/60'  
  option netmask    '255.255.255.0'
  option gateway    '107.209.154.46'
  list   dns        '8.8.8.8'
  list   dns        '8.8.4.4'
  list   dns        '2001:4860:4860::8888'
  list   dns        '2001:4860:4860::8844'
  option ipv6          1
  option defaultroute  1

config interface 'wan6'
  option proto         '6rd'
  option ifname        '6rd'
  option peeraddr      '12.83.49.81'
  option ipaddr        '107.209.154.41'
  option ip6prefix     '2602:300::'
  option ip6prefixlen  '28'
  option ip4prefixlen  '0'


# /etc/config/dhcp
config dhcp 'lan'
  option interface 'lan'
  option start '150'
  option limit '200'
  option leasetime '12h'
  # Not sure why I didn't use "list dns" for these as well.
  option dhcp_option '6,8.8.8.8,8.8.4.4'
  option dhcpv6 'server'
  option ra 'server'
  option ra_maxinterval 1800
  list   dns  '2001:4860:4860::8888'
  list   dns  '2001:4860:4860::8844'


I think that might be all relevant bits. Good luck!

(Ignore the ".1" and ".2"  I set up VLANs for fun at some point).

-- 
Tim Utschig <tim at tetro.net>