Hello,
I have LMT 5G MikroTik router and a static IPv6 /64 prefix assigned by LMT (provider in Latvia). Lately (for several months) I'm facing an intermittent problem: IPv6 connectivity stops working due to Duplicate Address Detected issue: 2a03:xxxx:xxxx:xxxx::/64 address (assigned by LMT) gets DIG status (I meaning invalid) and "Duplicate Address Detected" error. Sometimes I'm able to fix it by restarting MikroTik router and sometimes it doesn't help and I manage to fix it by disabling lte interface and enabling it few minutes later. Called LMT support, but they didn't see any issue on their side. Logs (including radvd logs) didn't show anything suspicious when issue occurred.
Finally, I decided to analyze network traffic and set /tools/sniffer/filter-ip-protocol to icmpv6 and started packet sniffer and restarted lte interface (causing the router to re-negotiate IPv6 address). Downloaded packet dump and opened in Wireshark. I was able to see Neighbor Solicitation message going to ff02::1:ff0:0 for entire /64 prefix assigned by LMT and one device responding with Neighbor Advertisement confirming that it has this prefix assigned. If I understand it correctly, this response is causing MikroTik router to give up and announce the entire prefix to be duplicate address and render IPv6 unusable. I found a MAC address of this responding device and it turned out to be Google Nest Hub smart display connected to my Wi-Fi network. I switched it off and duplicate address issue wasn't reproducible anymore.
So it looks like there are two problems: MikroTik router sends Network Solicitation for IPv6 prefix (received from lte interface in Router Advertisement from provider) to bridge interface instead of lte interface only (is it supposed to work like that?) and a consumer device from internal network (Google Nest Hub) responding to it with Neighbor Advertisement.
Is there a way to fix it rather than stop using Google Nest Hub? Maybe some configuration change in MikroTik would allow DAD to be performed only on lte interface? Or maybe I just need to somehow disable DAD?
Any help would be appreciated!
Many thanks,
Peteris