Dynamic IPv6 prefix: Any way to change the auto incremented subnet ID?

RouterOS General
1

I am using a RB5009 and getting an dynamic IPv6 ::/56 prefix, which changes each time, when my PPPoE connection reconnects to my PPPoE. Those dynamic ::/56 IPv6 prefix is assigned via ::/64 to my interfaces. Unfortunately ROS (7.16.1) uses some sort of automatic increment, which I would like to avoid.

In Linux, when using, for example, dhcpcd, you can set this subnet id, like “ia_pd 1 eth0/32”. The number 32 is being here the subnet ID. ROS seems to start from 00 and incrementing by 1.

Example:
ISP assigned this dynamic IPv6 subnet: 2a02:AAAA:BBBB:CC::/56
Via IPv6 Address, I’ve set on my interface: “::DEAD:BEEF:DEAD:BEEF/64”
ROS makes as result: 2a02:AAAA:BBB:CC00:DEAD:BEEF:DEAD:BEEF/64

Making changes or adding a new address to a new interface results in this:
2a02:AAAA:BBBB:CC01:DEAD:BEEF:DEAD:BEEF/64
This is being incremented on every change.

Is there any way, to modify or alter that subnet id?
Alter is not possible via “/ipv6/address/edit”, as changing the subnet ID results in “pool allocated address prefix bits should be zero” error.

2

IIRC it is currently not possible to manually control Subnet ID. Please contact mikrotik at https://help.mikrotik.com/servicedesk/servicedesk and let them know that you need this functionality.

3

Unfortunately, MikroTiks answer wasn’t really satisfying. They acknowledged, that currently, the subnet id cannot be set and will be maybe considered for future.

But they also told me this:

RouterOS has the tools to alter this behavior, either by implementing the scripting or manually assigning the subnet/prefix to the interface. This way, predictable and expected addresses can be assigned.

But I haven’t got any further information, what tools are meant.. so I have absolutly no idea, what they mean. Any ideas here?