IPv6 Address Pool decision

RouterOS Beginner Basics
1

I receive a /48 IPv6 Prefix from my Provider. This prefix is split into /64 for LAN assignment. This works, but I can’t choose the prefix the Mikrotik will generate.

Example:

 #    ADDRESS                      FROM-POOL  INTERFACE  ADVERTISE
 0  G XXXX:XXXX:d80b::1/64          init7      vlan50     yes      
 1  G XXXX:XXXX:d80b:1::1/64        init7      vlan90     yes

I don’t know how to define which one of the Interface will get the prefix with 1. It would be nice if I could put 50 and 90 corresponding to the VLAN Tags into the prefix. This was very easy to do on Ubiquiti EdgeMax.

Address Config:

/ipv6 address
add address=::1 from-pool=provider interface=vlan50
add address=::1 from-pool=provider interface=vlan90
2

You can’t, as discussed in several forum topics. It would be nice if you could do
/ipv6 address
add address=::50:0:0:0:1 from-pool=provider interface=vlan50

3

With /48 prefix it might even be possible (it isn’t if prefix is longer than 48=64-16 because ROS doesn’t allow setting bits in suffix which might overlap with prefix bits … even if they don’t). There’s a gotcha: one has to use the double colon “::” to mark the prefix and then use enough of “:0” to fill in the suffix … exactly as in example by @tdw.

4

Last time I tried, probably on 6.48.6, with a /48 it didn’t appear to work, may be different in v7.

5

Filling the prefix seems to also not work on v7:

;;; address pool error: bad preferred prefix! (1)
 1 IG ::90:0:0:0:1/64              provider      vlan90     yes