Recently we moved our infrastructure to a new datacenter and immediately we started getting ipv6 connectivity issues. At first I was blaming the ISP, but after a lot of troubleshooting I think it might has something to do with the Mikrotik gateway (CCR1009-7G-1C-1S+).
We have a regular /64 where ::1 is the gateway of the ISP and our mikrotik is ::2. The ISP routes an additional /48 subnet over the provided /64 to ::2. On the mikrotik we split the /48 into several /64 and advertise it in different vlans. We have a static route to 2000::/3 set to go to the ISP ::1.
With the ipv6-addresses disabled in the vlans, we can ping ::1 and the rest of the internet from the mikrotik without packet-loss or whatsoever. But when we enable the vlan gateway addresses the mikrotik begins to struggle. 'Flows' of packet-loss occur from hosts to the internet and vice versa. (defining 'flows': connectivity is ok and abruptly gone for a 10-20 seconds).
I can see in the IPv6 neighbors that the ::1 is changing regularly to status=failed and the mac address disappearing. I have no clue why, because when I ping ::1 from the mikrotik seems to be ok.
When keeping a ping running from the mikrotik to ::1 the connections seems to be failing less often (but still too often).
Do you have any ideas about what is going on here or suggestions on how to troubleshoot further?