Johannes Weber <johan...@webernetz.net> writes: > what are your experiences with dynamic IPv6 prefixes?
I have native IPv6 via Comcast, a cable company in the US. At first my IPv6 address got lost every few days (4 days if I recall correctly). After many frustrating rounds of hand edits to a dozen files in /etc and DNS zone file directory every time the address changed, I started to piece together what was going on. Basically the router, a Netgear 3700v4, while claiming to implement IPv6, was really just running highly buggy alpha quality firmware that was probably written by an outside contractor and never updated by Netgear. 1) the dhcp ipv6 renewals never occurred because the firewall wasn't allowing packets to destination port 546/udp (the dhcp6 port) through. Even after months of this being reported to Netgear they hadn't fixed it. Many other router manufacturers had the same problem. If you are losing ipv6 addresses and ipv6 simply stops even though the unit wasn't rebooted this is most likely the cause. 2) whenever the unit was rebooted it would get a new ipv6 address. Again this wasn't Comcast's fault. The IPv6 spec for dhcp doesn't use MAC address to identify the client. It uses a newly created method using what the RFC calls DUID. This can be generated by several methods one being a combination of the time the machine was *first* booted and the one of the unit's MAC address. The intention was to have only one identifier for the client even if it had several different interfaces (and hence multiple possible MAC addresses). It was also intended to prevent different units from sharing the same identifier in the case of a network card being moved to a different machine. The time of first boot would change, hence the DUID would be different. The intention was that once generated on a machine, the DUID would be written to a file or other store and used from then on. Router manufacturers seemed to have missed that fact because quite a few of them generate a brand new DUID every time the router boots. This is why the IPv6 address changes on every boot when running a buggy router (which is unfortunately most of the consumer routers running factory firmware.) I finally solved my problem with both the buggy firewall rules and the buggy DUID usage by installing aftermarket OpenWRT firmware on my unit. I now have semi-static dhcp6 issued addresses that don't change for many months at a time. >From your description, it sounds like you might be seeing issue #2 from above also. You might ask your ISP if they are seeing your DUID change or perhaps run a test where they compare the DUID before and after you reboot your router. As for the DNS changing perhaps once per year, I have a small shell script that runs on the client that registers its IP address in a dynamic DNS zone I created for this purpose. I use nsupdate with PKI security to secure the update. This also covers the case of laptops which might pop up on a different IP address several times a day. -wolfgang