IPv6 design, deployment, standards, and best practices.
Aaronchristopherc
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IPv6 Static Addresses? and more questions...

Sun Feb 12, 2012 11:08 am

I'm currently a student working on my Bachelor's in Network management. I have a few certifications and I'm working towards MCTS, and MCITP. Although I've had some experience (very little really) and I passed the exams for these certifications, I really don't know anything at all.

Anyway as I've gone through the study material for these certifications (Security+ Network+ and now 70-680 windows exam). I've become very interested in IPv6 and how it works.

So in order to resolve some of the addressing issues associated with IPv4 we've been using network address translation. So in reality most internal networks and home networks etc only have one public IP address, or very few public addresses.

With IPv6 in theory could each device have it's own public address?

Could this address then remain static? Windows 7 doesn't really take advantage of IPv6 technology yet, and while you seem to 'dual-stack' your Ipv4 address alongside an Ipv6 address. It appears that there is also a link-local address for IPv6 which would imply to me that it would work similarly to Ipv4 (using NAT on internal networks, with a separate public address).

However, given that the amount of addresses available in IPv6 is incomprehensibly large couldn't each device have it's own static public address? The implications of that are pretty staggering. Similar to a MAC address, but rout-able on the Internet. Could each device's NIC be hard-coded with a public IPv6 address?

If such a system was implemented could every device with IPv6-public addresses be setup for a direct-connection with other devices? In a global WAN ad-hoc network.

Sorry if my questions seem silly, I'm still learning. I am interested to here your thoughts, so thanks for any replies.

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Re: IPv6 Static Addresses? and more questions...

Sun Feb 12, 2012 11:32 am

You're on the right track with the "similar to a MAC address but routable on the internet". If you google for the term SLAAC, which is one way to assign addresses with IPv6, you'll find that it actually uses the MAC address to derive a usable IPv6 address. It takes the network portion (first 64 bits) and derive the last 64 bits by splitting the 48bit mac address in two and inserting the static 16 bit ff:fe between both halves.

That means that the same computer (same mac adress) will always have the same host-portion of an IPv6 address (the network-portion will of course change depending on where you are, network-wise). You could argue whether or not that is a good or bad thing, so there are for example RFC4941 defining something that's called Privacy Extensions which basically randomize the last last 64 bits instead of always derive them from mac.


And yes one of the foundation ideas behind IPv6 is no more NAT and a real routable v6 address to every device. The link-local address arent really equal to the v6 RFC1918 addresses since they cant be routed at all.

With that said, there surely WILL be NAT in v6 anyways because people will build like they did with v4 etc.
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Re: IPv6 Static Addresses? and more questions...

Sun Feb 12, 2012 2:10 pm

yes, in summary one of the whole ideals to ipv6 is that nat is not needed with the given address space.
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Re: IPv6 Static Addresses? and more questions...

Sun Feb 12, 2012 4:09 pm

Aaronchristopherc wrote:With IPv6 in theory could each device have it's own public address?

Yes, indeed. That is the goal as NAT introduces complexities into the network, especially with port translations involved sometimes. Having overlapping private IP ranges also is no fun to work with.

Aaronchristopherc wrote:Could this address then remain static? Windows 7 doesn't really take advantage of IPv6 technology yet, and while you seem to 'dual-stack' your Ipv4 address alongside an Ipv6 address. It appears that there is also a link-local address for IPv6 which would imply to me that it would work similarly to Ipv4 (using NAT on internal networks, with a separate public address).

Yes and no. The link-local address works like a 169.254.0.0/16 address, meaning that devices on the local subnet can talk to each other using these addresses, but they are not routable, and aren't translated anywhere. If you're not sure what I mean, try looking at it like a local network in your house where all computers use an address in the same range, connected by switch, but there is no internet uplink. It's just local communication.
Also, 'remain static' would certainly have advantages and is one of the design goals, but it also introduces privacy issues. Windows randomizes your IPv6 address by default for example, otherwise your MAC address could be tracked. So static is possible, but not required.

Aaronchristopherc wrote:However, given that the amount of addresses available in IPv6 is incomprehensibly large couldn't each device have it's own static public address? The implications of that are pretty staggering. Similar to a MAC address, but rout-able on the Internet. Could each device's NIC be hard-coded with a public IPv6 address?

No, but you're missing a point here: local subnet needs physical information (MAC address) to identify a device, but for (internet) routing, there needs to be a logical design. If you move a device to another location, it will likely need another IPv6 address. Public servers in America have other IP ranges than the ones in Europe and the ones in Asia. An internet router looks at the network information to route.

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Aaronchristopherc
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Re: IPv6 Static Addresses? and more questions...

Sun Feb 12, 2012 10:13 pm

Thank you for all the replies, greatly appreciated. I'm still pretty new, seems I've got a long, long way ahead of me in the networking world.

I feared there would be some privacy issues with IPv6 if all devices remained static, it's good to know that they've already taken that issue into consideration.

I'll stick around here and I'm likely to have plenty of more questions as time goes on. Thanks again for the information.

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