Fios IPv6 prefix changes on every router reboot?
dcostoy
Enthusiast - Level 1

Hi, all - I recently turned on DHCPv6-PD on my router on a whim (saw some chatter that the IPv6 buildout has been accelerating in the northeast) and saw that, indeed, IPv6 has been enabled in my area.

Everything seems to be working great.  However, I noticed that my delegated prefix changes every time I reboot my router. It would be nice if this were stickier to reduce the need for DDNS updates. (I guess I was somewhat spoiled by Hurricane Electric's fairly static delegation.)

Does anyone else (particularly with third-party routers) have any experience with this? Is this expected behavior? Is it something I should chase on the router side (e.g., maybe it is explicitly releasing it on shutdown?). I use an Asus ZenWifi ET8 mesh router system with latest stock firmware, if that makes a difference.

Thanks!

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Re: Fios IPv6 prefix changes on every router reboot?
Cang_Household
Community Leader
Community Leader

Using DDNS is a red flag for running publicly facing servers. The residential ToS explicitly prohibits the operation of servers of any kind.

Re: Fios IPv6 prefix changes on every router reboot?
dcostoy
Enthusiast - Level 1

Appreciate the heads up regarding DDNS. I wouldn’t  think it’s the kind of thing Verizon would take issue with for connecting back to my home network occasionally. I would expect it to be in place more to prevent commercial use/abuse of a residential product. But maybe I’m wrong.

I see you are very active on here. Do you have any insight on the PD assignment behavior by chance?

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Re: Fios IPv6 prefix changes on every router reboot?
smith6612
Community Leader
Community Leader

If your router generates a new DUID every reboot, you'll receive a new IPv6 prefix. I believe ASUS Routers generate the DUID based on your WAN MAC address, so make sure you're not using MAC Address Spoofing. Outside of that, it's possible Verizon right now just has a very aggressive release cycle for their delegated prefixes since the IPv6 rollout is still ongoing.

One option you may want to look for and disable is an option ASUS has in the IPv6 settings for releasing the prefix when DNSMasq exits. It should be a simple On/Off radio box somewhere in the IPv6 settings. Maybe it only appears if you're running ASUSWRT firmware (does Zen Mesh even use this?). It's been a while since I've messed around with ASUS Routers.

Also... there's nothing wrong with using DDNS even in a residential setting. It doesn't necessarily mean you're running servers, either. Maybe you just want an address to point a security camera app to in order to aid connections :).

Re: Fios IPv6 prefix changes on every router reboot?
dcostoy
Enthusiast - Level 1

Thanks!

I hadn't considered the possibility that this is just a temporary state during the initial rollout. Here's hoping 🙂

I ran into some search results that talk about a flag to release the prefix on exit (I think this is what you're referring to) but this doesn't seem to be a feature of the stock Asuswrt, just Merlin, and it's not supported on this model yet.  (I went so far as to try to set the flag in nvram directly, but I don't think the stock firmware even looks for it. ) So I may just be stuck with this behavior...

Will see if I can find any hint of what's going on in the dnsmasq logs.

Appreciate your reply.

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