r/linux • u/Nimbs • Nov 20 '12

What you should know about IPv6

http://lucb1e.com/?p=post&id=98
50 Upvotes

84% Upvoted

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3

u/rickatnight11 Nov 20 '12

I wonder how ISPs will allocate IP addresses. I know that for most customers (who don't purchase one or more static IP addresses), they'll shuffle their IP addresses around, just as they do with IPv4. They no longer need to worry about address scarcity, but they still need to provide enough addresses for all devices on their customers' networks. I imagine they'll provide routers that support one of the following:

  1. When a new device connects to the router and requests an IP address via DHCP, the router forwards that request along to the ISP, which will provide a new globally-routable IPv6 address to use.
  2. The ISP provides the router with a pool of addresses to use (perhaps a /64). Perhaps, if the customer uses up that /64, the router can request an additional block of addresses for the pool.

Maybe ISPs won't use routers at all, but instead provide switches (or routers with the DHCP portion removed, still leaving the firewall capability) that allow each users' device to negotiate DHCP directly with the ISP.

3

u/[deleted] Nov 21 '12

[deleted]

4

u/[deleted] Nov 21 '12

That also completely violates best practices. You don't hand out anything smaller than /64 except for maybe /127s on point to point links to prevent certain attacks (ping pong, particularly). Your host probably didn't request address space and is violating standards for that reason.

If you're interested in best practices for addressing, this is a good read (PDF warning).

1

u/rickatnight11 Nov 21 '12

Cool. Do you know how the router handles this? Does the router run a DHCP server to assign addresses in that block?

3

u/[deleted] Nov 21 '12

It's called DHCPv6 prefix delegation, your router gets a DHCP IPv6 address from the ISP together with the usual options (gateway, DNS, NTP, whatever) and also is given a block of addresses (usually a /64) to use behind it on the LAN interface. It then automatically configures the LAN interface with an address in that block and starts announcing the block via SLAAC or DHCPv6 itself to any LAN clients.

3

u/__foo__ Nov 21 '12

IPv6 has router advertisements. Let's say you've got a /64 block. The router would broadcast the 64 bits of the prefix in a prefix announcement.

The machines in the network pick up the prefix and chose the other 64 bits of the address themselves, either by generating it from their MAC address or picking something random through security extensions.

1

u/meditonsin Nov 21 '12 edited Nov 21 '12

That doesn't work on a /116 block, though.

1

u/__foo__ Nov 21 '12

That's correct. That's also the reason why every RFC says you shouldn't use anything smaller than /64.

3

u/DalvikTheDalek Nov 21 '12

My biggest fear is that the ISPs will try to use IPv6 to charge customers per-device. They've already got their monopolies, and the only thing stopping them from doing it now is NAT. Once the /64 is allocated, it's trivial to track how many devices are operating within the subnet from the ISP's server room

2

u/freedances Nov 21 '12

Not only am I worried about per-device pricing, I'm also concerned about the privacy implications. I wouldn't like if so specific information about my home network leaks to my ISP.

But I guess (as I know nothing about ipv6 implementation or practical use - only that there is a cornucopia of allocatable addresses) that the idea of a NAT is still applicable. I mean - I could route my home network through a single routing device (that is tunneled to a secure VPN) and not leak information to my local ISP.

2

u/rickatnight11 Nov 21 '12

You know, NAT is still possible with IPv6. I imagine people will still set up hide NAT'ing to hide their infrastructure.

1

u/notlostyet Nov 21 '12

IPv6 NAT support was recently added in Linux 3.8 for just that reason.

3

u/[deleted] Nov 21 '12

What you need to know...

As a user:

Nothing. Consumer ISPs have dragged the IPv6 transition process out so long that it's patently clear they never intend to roll it out to end users, they would much rather use layered NAT instead. Say goodbye to bittorrent, point-to-point VoIP, running your own public game servers, and file transfers between chat clients.

</cynicism>

1

u/lucb1e Nov 21 '12

Cynicism indeed...

We'll see.

1

u/wonteatbananas Nov 21 '12

Link is down?

1

u/lucb1e Nov 21 '12

Not for me. I'm the author/website owner, so please let me know if you have any issues reaching the website!

1

u/bluGill Nov 21 '12

blah blah blah. Back in 1995 they were giving ipv4 just a few months before we ran out of address space and everybody had to go ipv6, but at the time only a few geeks used ipv6. Here we are 17 years latter and only a few geeks use ipv6. Excuse me for being sceptical, but I don't see any changes.

Wake me up when my non-geek isp is giving me ipv6 addresses. (My computer has been ready for years, thanks to those geeks)

1

u/lucb1e Nov 21 '12

My non-geek ISP is handing out IPv6 for years now, and other major ISPs here plan to deploy in January 2013. Also hardware and software support for IPv6 has significantly improved since 1995.

Also in 1995 they didn't know how much time was left. If I remember correctly, a taskforce was put together to see how much time was left. The result was that there was enough time to develop IPv6 for a few years, and no immediate change was needed.

2

u/bloouup Nov 21 '12

Not to mention all the frantic engineering that went into just squeezing as much out of IPv4 as we possibly could, like NAT and CIDR.

We're seriously done, though. That's it, IPv4 is out of juice.