[olug] IPv6

Lou Duchez lou at paprikash.com
Thu Jul 4 05:29:36 UTC 2013

Anyone have a handle on IPv6, is anyone using it?  I'm finding lots of 
information about IPv6 on the Internet, but not a lot about what to 
expect trying to actually use it.  So I thought I'd ask you.

1)    I have found a page that says IPv6 IPs will predictably follow 
this format: bits 1-48 are assigned by my ISP, bits 49-64 are for me to 
set up distinct networks (subnets), and 65-128 are for device 
assignments on my networks.  Is that how it really works?

1a)    So any device that needs to get to the Internet will need an IPv6 
address that starts with the 48 bits assigned by the ISP, right?

1b)    If the first 48 bits of all Internet-accessing device IPs are set 
by the ISP, it sounds like it will be a gigantic pain in the hinder when 
I change ISPs: changing ISPs will mean changing 128-bit IPs.

2)    NAT ceases to be an issue for normal routing, right?  My 
computer's IP as seen by other people on my LAN will be the same as my 
computer's IP as seen from across the Internet.  I will still need to go 
through a router to actually get to the Internet, there just won't be 
any NAT happening.

2a)    This means that I need to explicitly add rules to my firewall to 
provide the protections inherent under NAT: incoming traffic to my 
networks is allowed only if ESTABLISHED / RELATED or if I have a port 
open to that device.  Come to think of it I've already got those rules 
under IPv4 so maybe I won't need to do anything conceptually different.

2b)    What does this do to networks with multiple gateways?  I've got a 
friend's network set up to use an alternate connection to a different 
ISP in case the primary one goes down.  This isn't a problem under IPv4 
thanks to the magic of NAT, but without NAT, how could I pull that off?

3)    At present, in IPv4, I get a dynamic IP from my ISP.  Under IPv6, 
will those first 48 bits be static?

3a)    Any privacy concerns with that?  Connecting via a non-fixed 
address is "safer" if you're doing anything where anonymity is in your 
best interests.

4)    To set up dhcpd on my Linux box, I'm going to need to know the 
first 48 bits, and factor that into my dhcpd config files, right? 
(Either that or else write some sort of script that parses my router's 
IPv6 address to get those first 48 bits.)

5)    If I understand correctly, the first 16 bits of an IP address will 
specify the ISP.  That allows for only 65536 ISPs, minus whatever IP 
ranges are used for other purposes (your fec0's and the like).  Isn't 
that, uh, begging to run out?  There are thousands of ISPs in the United 
States already.  Or will only a few of those 65536 be given out to the 
US and those thousands of ISPs will share the first 16 bits?

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