Hello,
Routeros 6.38.1 PPPOE Server with DHCPv6 PD enabled.
IPv6 pool: Prefix xxxx:yyyy::/52 Prefix length: 64
Client: Ubnt Airos6: DHCPv6 client on pppoe, Prefix Delegation with statefull DHCPv6 Server, IPv6 Prefix Length: 64 on lan.
Everything works correctly with IPv6, but on PPPOE Server i get the above error: pool6 refused acquire: bad preferred prefix! (6)

What's wrong?

I've got similar error:
pool6 refused acquire: pool not found:


And I have the pool defined in both, server and client?

Any idea?

Thanks in advance

same issue, DHCPv6 server is broken

I have a /56 from DHCPv6 client. Trying to hand out this /56 with DHCPv6 server, keeps getting this error in log

Problem is not in Mikrotik dhcpv6 server, when you set prefix length in ubnt lan interface to /64 it requests from Mikrotik /64 and that is != /60 configured in Pool, that's why error happens.
If you configure ubnt lan to request /60 and set stateless dhcp, there is no error in log, prefix is accepted and /64 is assigned to lan interface of ubnt.

OP specified that the prefix-length in the pool is /64, not /60, so that may not be the problem for him.

I reject your reality and substitute my own!

After update to 6.43.4 the ubiquiti client doesn't get prefix anymore and router throws above error continuously.

Same problema here with CPE Intelbrás WOM 5000 MIMO. CPE is set to AUTO but get /64 instead of /56.

After update to 6.43.4 the ubiquiti client doesn't get prefix anymore and router throws above error continuously.

same here

Found this post after searching for same symptoms - Did anyone find a resolution?
Thank you

Found this post after searching for same symptoms - Did anyone find a resolution?
Thank you

Nothing yet!

For anyone wondering, we tried to downgrade the RouterOS on hEX Lite with this problem (we were running 6.43.4). The router itself didn't downgrade (consumed the ROS package - ?) but the DHCPv6 client started working. So it might be worth a shot for you till this is fixed.

Any news on that?

Any update on this?

Just wanted to let folks know we kept banging our head on this problem. Turns out if you put "0" in for the IPv6 prefix length of the airMax settings then it just honors what the Mikrotik DHCPv6 server/pool offers.