[colug-432] IPv6

[Richard Hornsby]

(Sorry moderators - trying again from the correct account.)

I understand that IPv6 is a 128 bit address, instead of the outdated 32 bit system that we're using today, which has more or less run out of space.  What I'm less clear about is how to use it properly, and how to interpret that really long string into something meaningful.

en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
	ether f8:1e:df:d7:1b:80
	inet6 fe80::fa1e:dfff:fed7:1b80%en1 prefixlen 64 scopeid 0x5
	inet6 fd5d:4ffd:7d1b:1:fa1e:dfff:fed7:1b80 prefixlen 64 autoconf
	inet6 fd5d:4ffd:7d1b:1:8db7:5b1c:f3b0:3bad prefixlen 64 autoconf temporary
	inet6 2605:a601:2a1:d101:fa1e:dfff:fed7:1b80 prefixlen 64 autoconf
	inet6 2605:a601:2a1:d101:207b:59de:cf87:ce3f prefixlen 64 autoconf temporary
	inet 192.168.1.7 netmask 0xffffff00 broadcast 192.168.1.255
	media: autoselect
	status: active

I get "192.168.1.7" and can generally remember that well enough.  I thought that an IPv6 address had something to do with the MAC address, but I'm not seeing it here (some pattern of bytes in common, but not sure it means anything?), and I'm unclear on why there are so many IPv6 addresses configured on this (OSX, admittedly) wireless interface on my home network.  I'm not doing anything special, just standard DHCP(?) provided by the google fiber router box thing that's doing IPv4 NAT as well as IPv6 routing.

When I look at what my public IP is showing up as, I get

"Your public IP address is 2605:a601:2a1:d101:207b:59de:cf87:ce3f"

which shares the same first 8 bytes (2605:a601:2a1:d101) as one of the inet6 addresses on the interface (but the final 8 seem to come from?)  I also notice that the last ipv6 address on the interface matches the public address.

I'm really confused, and having a hard time finding information somewhere between IPv6 for dummies "computers use bits, that means 1s and 0s" and the super technical stuff.  Can anyone break it down?  If you understand the IPv6 stuff, do you _really_ type in that really long string in cases where DNS isn't present or available?  

Speaking of that - I sometimes test connectivity or DNS by using 8.8.8.8 (or, back in the day -- 128.146.1.7 / 128.146.48.7 ;) ) -- easy to remember.  How does anyone remember what the IPv6 equivalent of that (or anything else) is?