Re: IPv4 v IPv6
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On Monday 17 June 2019, Gene Heskett <gheskett@shentel.net> was heard
to say:
> How is that resolved, by unroutable address blocks such
> as 192.168.xx.xx is now?
Yes, IPv6 does have such allocations. The first 64bits is network
block, then the last 64bits are your local machine.
fc00:: is the non-routed network. RFC1918 equiv.
fe80:: is the link-local address which is not routed at all, it is
used solely between your device and the router. Personally, I would
have combined these two, but when IPv6 was being built they didn't
ask me.
Your device will always have an address built of its MAC address, with
FF FE in the middle of it, for every network block including link
local, like this:
# ifconfig
enp1s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.85.86 netmask 255.255.255.0 broadcast
192.168.85.255
inet6 fe80::beae:c5ff:fe66:ec70 prefixlen 64 scopeid
0x20<link>
inet6 2691:178d:8d80:efd:f92f:91cf:1240:640d prefixlen 64
scopeid 0x0<global>
inet6 2691:178d:8d80:efd:beae:c5ff:fe66:ec70 prefixlen 64
scopeid 0x0<global>
ether bc:ae:c5:66:ec:70 txqueuelen 1000 (Ethernet)
These show the three entries which should always exist. The first is
the link-local address built from the MAC. Second, the allocated
network from my ISP, with a randomized local address for security
purposes.
The third entry is the global network address and the local MAC based
address. Someone realized broadcasting your MAC address is not
particularly secure, so the randomized interface address has become
the norm. This third address is what you would put in your hosts
file.
> how do the other machines on my local net, advertise their presence
> to the other machines on my local net. So I can still ssh -Y
> vna.coyote.den for instance, if I can ever make ssh work to a
> win-10-home edition box.
You do so by either making a static fc00:: entry, or by knowing your
global network you can then just splice on the MAC local address
since the MAC local doesn't change.
Unfortunately, because DHCP6 is really dynamic, and my ISP changes the
network blocks every once in a while, having the global network
entries and MAC local addresses in the hosts file has been a complete
waste of time.
Having fc00::MAC as a non-routed local RFC1918 default would have been
sooooo much easier, but no, IPv6 was not designed by network
engineers. It was designed by old AT&T phone engineers who were
pissed they were being put out of a job by competition, and wanted to
curse the world with increased complexity where none was needed.
- --
You may my glories and my state dispose,
But not my griefs; still am I king of those.
--- William Shakespeare, "Richard II"
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