In the current implementation of PVC/PCS, it is not possible to assign a subnet of IP addresses for both IPv4 and IPv6 address types to containers or virtual machines in host-routed mode.
This functionality is planned to be included in the future PCS releases in scope of a feature request with internal ID PSBM-21242.
As a workaround, it is needed to specify each IP address separately via
--ipadd vzctl call in a loop. Real-life example:
# for i in `seq 1 11`; do vzctl set 101 --save --ipadd 2a03:8180:1001:4f::$i/64; done