Question: How does a PDN connection obtain additional IPv6 prefixes when the default /64 prefix is not used?
Option 1: The UE uses IPv6 stateless autoconfiguration to generate additional prefixes.
Option 2: The GGSN/PDN GW allocates additional prefixes from a locally provisioned pool without any request from the UE.
Option 3: The UE uses DHCPv6 to request additional IPv6 prefixes from the GGSN/PDN GW or an external PDN.
Option 4: The PDN connection is allocated only one /64 prefix and cannot obtain additional prefixes.
Explanation: When a single network prefix shorter than the default /64 prefix is assigned to a PDN connection, the UE can use DHCPv6 to request additional IPv6 prefixes from the GGSN/PDN GW or an external PDN. This allows the UE to obtain more address space for its PDN connection.