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Author Topic: Do IPv6 address assignments ever change?  (Read 5944 times)

PatrickDickey

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Do IPv6 address assignments ever change?
« on: April 17, 2015, 03:59:09 PM »

Hi everyone,

My question may seem strange, but here it is. If I set up a local network with IPv6, and all of the devices get their IPv6 address through DHCPv6 or SLAAC, will they ever get a different IPv6 address (assuming that they remain on the network permanently)? I know in DHCPv4, you're not guaranteed the same IPv4 address, as it's first come first served. So is this the same with IPv6?

The reason I'm asking this is because there's a linux based server (Amahi) that's looking into implementing IPv6 in their software. So if the address won't change, then it shouldn't need to be configured statically. So essentially they'd just have to enable it. Otherwise, they'll have to have inputs for a static IPv6 assignment on their configuration page.

Thanks and have a great day. :)
Patrick.
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evantkh

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Re: Do IPv6 address assignments ever change?
« Reply #1 on: April 17, 2015, 06:28:41 PM »

IPv6 assigned by SLACC with privacy extension changes over time because it is randomly generated. To get a static IP, your need to make sure the privacy extension is disabled.

For DHCP, it actually depends on the settings of your DHCP server. There is something called address reservation.

However, if your IPv6 prefix is assigned dynamically by your ISP, you should not set it statically on your device.
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PatrickDickey

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Re: Do IPv6 address assignments ever change?
« Reply #2 on: April 18, 2015, 05:09:46 AM »

Ok, so I'm going to ask a bunch of questions (stupid, maybe :) ). The goal here is to be able to explain this to the developers of the Amahi Server, as they're not very familiar with how IPv6 works.

1. Regardless of whether a device gets an IPv6 address from an ISP (or a service like TunnelBroker or Sixxs), does it generate a link local IPv6 address on each interface?

2.  If the answer to #1 is yes, can other devices on the same LAN ping that device by it's link local IPv6 address?

3. If the answer to #2 is no, are there any IPv6 addresses that are generated for the LAN, regardless of whether the device(s) get a routable IPv6 address (and to be clear, routable IPv6 address is a correct term to describe the IPv6 address that an ISP or tunnel broker provides)?

4. The Amahi server system uses a client to update the IPv4 address that's assigned by the ISP to their network (you have a personalized sub-domain in their "yourhda.com" domain). Since the system is on Linux (Fedora or Ubuntu, depending on which version they're using at the time), is there an easy way to send an IPv6 address if it's there (meaning the one assigned by an ISP or tunnel broker)? Or would it just send whatever they get, and they'd have to filter out any fe80:: based ones?

I also realize that you can't ping a link local address via the computer's name, but that's a minor issue which can be worked around later.

Thanks for your help, and I'm sure I'll have more questions later on. :)
Patrick.
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cholzhauer

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Re: Do IPv6 address assignments ever change?
« Reply #3 on: April 18, 2015, 06:06:53 AM »

1.  As long as it's enabled.  Just like ipv4, you can pick and choose which interface has ipv6 enabled

2.  Yes, won't cross routers though
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