Community Fibre and losing IPv6?

Has anyone else had this problem. I have had Community Fibre flush Mac addrssses and I find my IPv6 (using a Ubiquity UDM router) will provide valid IPv6 addresses for a few days to my Windows 11 PCs and iPhones but then it just stops. Using various "what's my ip" web sites to check if a client has a valid ipv6 address.

Not sure what is going on here?

I have no issues with them using my MikroTik Router, they provide my router with a /48 address and the router and devices do the rest.

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Paul

Thanks - Aside from the 48 Prefix setting what other settings do you have for IPv6?

Mine are:

Client address assignment: DHCPv6 (not SLAAC)
DHCPv6 Range: Start: ::2 and Stop: ::7d1
Leasetime 86400
DNS Server: Auto
Router Advertisement: Auto
RA Priority: High
Allow SLAAC: Yes

This is an issue with the UDM and you'll need to query the UDM to determine what's going on. Compare the status when it's working versus when it's failed.
* Does the UDM still have an external IPv6 address on its WAN port? (This might just be a link-local address though)
* Does the UDM still have an IPv6 default gateway pointing to the other side of the WAN link? (Again could be link-local)
* Are you able to send IPv6 pings from the UDM itself, e.g. to 2001:4860:4860::8888 (Google DNS)?
* Does the UDM still have a delegated prefix received via DHCPv6?
* Has the UDM still configured an IPv6 address on the LAN side network?
* Is the UDM still sending Router Advertisements with the LAN prefix on the LAN side network?

It sounds to me like the process of renewing the lease on its delegated prefix isn't working. Whether that's UDM's fault or CF's fault is hard to say, but if you can run a different router for a few days (e.g. whatever CF provide, or a PC running pfSense) and that works OK, it would point the finger at UDM.

I use a MikroTik Router running RouterOS which was a pian to setup, which is why I haven't touched it since it was all setup and working.

I just setup DHCPv6 Client that requests for an IPv6 Prefix and that is it.
My router gets given AAAA:BBBB:CCCC::/48 then the router creates its own AAAA:BBBB:CCCC::1/64 (this is the routers public IPv6 Address) and stores that in the IPv6 Address Pool.

I also use Neighbor Discovery (ND) on the LAN Side (bridge)

I then setup the routers DHCPv6 Server where it provides its own internal IPv6 Address (starting with fe80 based off its MAC Address of that port) as the primary DNS Server + a few fast DNS Servers as backup, I don't use CFL DNS Servers.

My PC (Windows) gets given 2 [AAAA:BBBB:CCCC:D:EEEE:FFFF:GGGG:HHHH] IPv6 Addresses (Public + Temporary one)

I think that was all that I setup, it was over a year ago that was setup and its been connected ever since.

Also https://ipv6-test.com/ (click cancel when it asks for a Windows CERT) gives me a score of 19/20 - I lose 1 point due to there is no Reverse DNS (hostname) setup for the IPv4 + IPv6 Addresses.

All their Public IPv4 and IPv6 Addresses are detected as being Static Addresses, just that they are using them dynamically, but they are sticky, I have had my IPv4 Address for over a year and still kept it when my router was turned off all day when installed new cables etc.

But that is all that I did, basically you should only need to ask them for a prefix address and you let your router do the rest.

If you get your IPv6 Address fine and it still fails to work over IPv6 then you may need to check if the routing path is all setup right.

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Paul

I have my MikroTik Router just request for an IPv6 Prefix (over DHCPv6 Client) and get given a /48 Address and my router does all the rest and works fine.

I don't even use their DNS Servers, I use my own and fall back to Cloudflare and Google DNS Servers.

So my guesses is that it might be a Unifi issue and something is not setup right.

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Paul

Thanks so much - yeah that maps to what I have and it will work for a bit then just stops working (across PC's and iPhones alike) - rebooting both the ONT and the Ubiquiti UDM won't restore it. If I call Community Fibre and have them flush the MAC addresses it will then work again - for a bit. I'm at a loss as to what is going on!

In reply to a post by pdampier:

I'm at a loss as to what is going on!

If you want to debug this, i.e. provide enough information to UBNT and/or CF as to what's going on so that they can resolve it, then you could start with the checklist of things I gave you.

(Additional item for the checklist: on your PC's and iPhones, when the problem occurs, check whether they still have an IPv6 address and gateway, and also try a tracert to 2001:4860:4860::8888 - it should go at least one hop to the UDM)

If you just want to fix it and move on, then it sounds like replacing the UDM with another device may be required. (I'm presuming you've already checked the UDM's firmware is up to date)

If you just want to prove it without spending money first, then try temporarily using an old PC with two NICs running pfSense as your router. That's actually a pretty decent long-term solution too, but you'll probably want to buy a low-power box if this is what you decide to use.

Edited by candlerb (Tue 28-Nov-23 12:30:29)

Thanks and sorry somehow missed your original reply. Yes my next step here is to replace the UDM with the Comminity Fibre Linksys router and run with that for a few days. Only issue there is it effectively takes down my home network and I'll only have limited WiFi coverage over the home (current UDM drives 2 additional APs) and the lniksys doesn't have enough ports to drive my central switch and all the other wired links that currently go into the UDMS wired ports.

Some commentsi inline in the quote:

In reply to a post by candlerb:

This is an issue with the UDM and you'll need to query the UDM to determine what's going on. Compare the status when it's working versus when it's failed.
* Does the UDM still have an external IPv6 address on its WAN port? (This might just be a link-local address though)

There is no place in the UDM ui that I have found (asked on UDM forums too) that shows a IPv6 address at all. No one else seems to know where it would be displlayed either. I prob need to SSH into it.


* Does the UDM still have an IPv6 default gateway pointing to the other side of the WAN link? (Again could be link-local)

See above


* Are you able to send IPv6 pings from the UDM itself, e.g. to 2001:4860:4860::8888 (Google DNS)?

Will get that once i SSH in.

* Does the UDM still have a delegated prefix received via DHCPv6?

Not sure how I'd find that out?

* Has the UDM still configured an IPv6 address on the LAN side network?

PCs seem to pick up preferred ipv6 addresses once the problem hits almost like the UDM stops supplying them but like I say I reboot on the UDM doesn't fix this.

* Is the UDM still sending Router Advertisements with the LAN prefix on the LAN side network?

Not sure how to find that out?

It sounds to me like the process of renewing the lease on its delegated prefix isn't working. Whether that's UDM's fault or CF's fault is hard to say, but if you can run a different router for a few days (e.g. whatever CF provide, or a PC running pfSense) and that works OK, it would point the finger at UDM.