DHCP-PD configuration assistance

Hi there,

The following configuration snippet successfully requests a /56 IPv6 prefix from my ISP (IPv4 config also works fine):

vyos@vyos# show interfaces pppoe
 pppoe pppoe0 {
     authentication {
         password XXXXXX
         user XXXXXX
     }
     default-route auto
     description OUTSIDE
     dhcpv6-options {
         pd 0 {
             interface eth3 {
                 address 2
                 sla-id 1
             }
             length 64
         }
     }
     firewall {
         in {
             ipv6-name OUTSIDE-IN-6
             name OUTSIDE-IN
         }
         local {
             ipv6-name OUTSIDE-LOCAL-6
             name OUTSIDE-LOCAL
         }
     }
     ipv6 {
     }
     mtu 1500
     source-interface eth4.10
 }

Version: VyOS 1.3-rolling-202101010217

eth3 is assigned the full /56 prefix (see below). How do I assign it just a 64? I’m planning to add more VLANs once this is working. Cheers

vyos@vyos:~$ show interfaces
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface        IP Address                        S/L  Description
---------        ----------                        ---  -----------
eth1             -                                 u/D
eth2             -                                 u/D
eth3             192.168.43.1/24                   u/u  INSIDE
                 xxx:xxx::2/56
eth4             -                                 u/u
eth4.10          -                                 u/u
eth5             -                                 u/D
eth6             -                                 u/D
lo               127.0.0.1/8                       u/u
                 ::1/128
pppoe0           xxx.xxx.xxx.240/32                 u/u  OUTSIDE