Re: IPv4 v IPv6
On Monday 17 June 2019 11:39:12 am Curt Howland wrote:
> 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.
Me neither, but then I've had it amply proved that my oar, in terms of
steering this ship of state, isn't even the equ of a broken toothpick.
Sigh...
> 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.
>
I am lucky, my ISP uses the connecting MAC to translate to a fixed ipv4,
that has not changed in 6 years. So my web page address in my sig has
not changed in 6 years even if I swap the router as my standby unit has
the good ones MAC cloned into it. So I get a registered STATIC domain
for almost zip compared to the cost and monkey business associated with
keeping a dynamic address uptodate globally.
> 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.
Chuckle, I subscribe to that theory myself.
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
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