I've recently encountered issues getting IPv6 working with my ISP. On investigation, I believe this is due to "rapid commit" in DHCPv6. This packet capture shows the issue, captured by my router:
The initial DHCPv6 solicit from my router has the "rapid commit" option in the packet, however the DHCPv6 "advertise" received from my ISP does not have "rapid commit" set, so my router treats it as a normal 4 packet DHCPv6 process, and continues to send "requests" as if it had not enabled "rapid commit" in the initial solicit... until the solicit times out.
It's entirely possible this is my ISPs issue, in that it is not handling "rapid commit" correctly. However, as this seems to be a buggy feature I really think we should have the option in Router OS to disable it... or set a flag to always act as if it is set in server responses. Either of these would allow me to resolve my issue, but as it stands I can't control my router's behaviour or my ISP's DHCP server's behaviour. Also... good luck getting through to anyone clueful enough at a large carrier to resolve this sort of issue.
While looking for a solution to my issue, I've found a couple of other users with the same symptoms:
https://www.reddit.com/r/mikrotik/comme ... t_timeout/
I've tried old versions of Router OS back to 6.35.4, and I'm currently running 6.44Beta40. All versions I've tried seem to have this same issue. I have an RB3011UiAS, so cannot run older code that does not have rapid commit forced on.