Recently I have been deploying IPv6 through out in our network and experiencing some difficulties when trying to reach some destinations. My setup is attached in this post.
The issue I'm facing is I cannot ping from R1 to R2 loopback address. It shows no route to host. But I can ping to R1 loopback address from R2 without any issue. For R1 and core 2 we are using mikrotik and R2 and core 1 we are using cisco. From core 1 and core 2 i have no difficulties to ping anywhere in the network. I have hard coded the link local mac address of R2 to see if the problem exists because of mac address but found nothing. There is no ospfv3 route learned by core 2 as well. But it is able to reach R2 and I had to add a default route to reach R2 loopback address in R1. Please explain what's the difference in between core 2 and R1 and what's makes core 2 to reach the destination and R1 not. I can reach all other mikrotik routers loopback in network but not cisco devices. Below is the response I received from mikrotik support and I'm not satisfied with the support.
"It shouldn't be reachable either ( core router 2). Unless you have on some other router enabled RA, and core router gets default route (which is not visible in routing table), or because of route cache, where old cached entry is saved"