Re: IPv6, was IPv10

"John Levine" <> Thu, 29 December 2016 16:19 UTC

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Date: 29 Dec 2016 16:18:37 -0000
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From: "John Levine" <>
Subject: Re: IPv6, was IPv10
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>>No, we are obviously not ready with [3] yet,
>I don¹t understand this statement, since thousands of access providers and
>enterprises are running IPv6.

There are still all sorts of places that things that are easy and
painless with IPv4 are much too hard with IPv6.

Here's an example: in my house I have a network behind a router
connected to Time-Warner cable.  T-W gives me one IPv4 address so my
router NATs.  I configured it once to use and it works
great.  I have a separate server running DHCP and DNS and some other
local services.  It hands out fixed addresses for devices like
printers and the backup server, and dynamic ones for devices like
phones.  The DNS cache (unbound) knows names for all of the fixed
address devices, and handles queries from devices on the LAN, which
are all configured by DHCP to use it.  This took about an hour to set

T-W apppears to give me a /48 of IPv6 addresses, so every time my
router reboots it picks a /64 at random out of that /48, and all of
the IPv6 addresses on my LAN change.  There is probably some way to
tell the router, a linux based Ubiquiti Edgerouter, to pick the same
v6 /64 every time, but I can't figure out what it us.  It was hard
enough to reverse engineer the router config to make SLAAC work at
all.  Maybe I should use DHCPv6, but I'd have to figure it out on the
server side, and then see how well all of my devices support it.

If IPv6 is going to be useful, I also need a v6 DNS cache.  Since the
global v6 addresses are unstable, I set the cache to answer on link
local address FE80::2, and set the router announcements to announce
it.  All set?  Nope.  That's a link-local address so the address is
actually FE80::2%xxx where xxx is each device's LAN interface, and
devices do a generally rotten job of appending the interface name to
the address they get from SLAAC.  I might be able to use ULAs but I
have no idea how well ULAs actually work and how I would set them up
on my servers, so my DNS cache is at and will stay there
for the indefinite future.

Perhaps there are ways to deal with all of these, but I am a fairly
sophisticated network operator, and I doubt I am all that much less
competent than everyone else.  So when people say IPv6 still isn't
ready for prime time, they're not kidding.