Solved - delegated IPv6 prefix not acquired

[9axqe]

Hello all,

I just solved an annoying issue with IPv6 prefix delegation and thought I'd share this, as it did cost me some time.

In my setup, OpnSense is not the WAN router, it's acquiring the IPv6 prefix from the WAN router. Well, it was supposed to be doing this and but it wasn't working. Sometimes it was, sometimes not, very strange.

So I ran a packet capture on the WAN interface and discovered I had a rogue DHCPv6 server on my network. It was a small TP-Link router running openwrt I use as a dumb switch (or I thought I was using as a dumb switch). DHCPv4 was disabled, DHCPv6 was not somehow (I could have sworn I had it turned off).

The strange thing is that this only bothered OpnSense, all other devices somehow were ignoring the rogue DHCPv6 router, only OpnSense was very confused by it (and maybe rightly so)...

Just in case someone else runs into the same issue in the future.