[TriLUG] IPv6 equivalent to dhclient list

[Aaron Joyner]

>From the router, I would expect ipv6 neighbor discovery to show all of the
hosts on the network, basically all the time?  Apparently in practice
that's not the case.  It'd be great if someone would read and summarize the
RFCs <https://tools.ietf.org/html/rfc4861>, and if necessary the code of a
couple implementations (linux, *bsd), then provide some example data.  I
realize I'm usually that guy, but I'm too busy tonight.  :)  Perhaps NDPMon
<http://en.wikipedia.org/wiki/NDPMon> can give you the data you want in a
persistent file on disk?

"autoconf temporary" equates to a dynamically chosen ipv6 address that
doesn't expose your MAC address when you communicate across the Internet.

If you want reliably addressable names of machines, without the hassle of
hard-coding addresses*, you probably *should* be running DHCP over V6.
Note that these names are still "network specific", because (as you noted)
the prefixes change with the locality, your laptop would have more than one
name:
asjlaptop.joyner.ws
asjlaptop.myinlaws.tld

I feel like IPv6 had some neat tricks up it's sleeve for solving this, but
I don't remember them off the top of my head.  Perhaps someone else will
chime in, or I'll find time to dig into it later.

Aaron S. Joyner

* - I allocate :1, :2, :N to some machines on my network, then assign names
to those IPs, so when I change network cards or motherboards (I've been
doing a surprising amount of that lately at home :-/ ), I have one less
thing to update.

On Tue, Jan 6, 2015 at 10:46 PM, Alan Porter <porter at trilug.org> wrote:

>
> My current first-pass experiment:
>
> - Read the /var/lib/dnsmasq.leases for lease+MAC+IPv4+hostname
> - Run "ip -6 neighbor show" for MAC+IPv6
> - Correlate MAC addresses.
> - Show it all in a table, using dnsmasq leases as the master.
>
> So I am looping over the IPv4 addresses and then looking for
> IPv6 addresses with matching MAC addresses.  The disadvantage
> of that logic is that an IPv6-only host will not show up in the
> list.
>
> Overall, it's hard to predict which hosts will have IPv6 addresses
> and which will not.  It just has to do with which hosts have been
> doing IPv6 stuff recently.
>
> It's also weird to see that a few hosts have IPv6 addresses in the
> fe80::0/10 (link-local) range.
>
> And weirdest of all, my MacBook has two 2001::0/16 addresses!  OSX
> "ifconfig" says that one of them is "autoconf" and the other is
> "autoconf temporary".  I was NOT expecting that!
>
>
> Alan
>
>
>
>
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