 In the majority of cases, the IP address configuration leads to a dynamic allocation of the IPv4 address or IPv6 prefix to a UE. However, the 3GPP architecture also makes it possible to assign a static IPv4 address or IPv6 prefix to the UE. Both modes of IP address assignment are described in detail. 4.4.2 Stateless IPv6 Address Autoconfiguration IPv6 Stateless Address Autoconfiguration (SLAAC), as specified in [22, 23], is the only supported IPv6 address configuration mechanism by 3GPP specifications for a 3GPP access and a trusted non-3GPP access. These cover S5-, S8-, and S2a-interfaces. Stateful Deploying IPv6 in 3GPP Networks HLR/HSS (Static addressing per APN per subscriber; from external PDN address space) Gr/S6a/S6d Addressing scope ((Q)) GGSN/PGW (S)Gi and tunneling to external PDN/ISP External SGSN/MME Gn/S5 Internal Pools DHCP Server Router Pools Client/ Operator's Internet Relay/ 'Server' AAA Server Pools Client Figure 4.20 IP address management methods and places for non-transparent access case. Table 4.5 IPv4 and IPv6 address management methods available in core network according to 3GPP standards [25] Management method Remarks PGW internal pools IP addresses and prefixes are assigned from PGW internal pools. The used pool may also be selected using for example, external AAA or DHCP server. The PGW may also implement a DHCP server function. HLR/HSS subscription IPv4 address and/or IPv6 prefix can be configured per APN and profile per subscriber. There can be multiple static configurations for one subscriber. External AAA server Multiple methods are available. An IPv4 address and/or IPv6 prefix is assigned by the AAA server, or the AAA server names the PGW internal address pool. External DHCP server PGW as a DHCP client or relay queries an external DHCP server for an IP address or an IPv6 prefix (including prefix delegation). External router The APN is terminated to an external router, which uses some mechanism to assign IPv4 address and/or IPv6 prefix. Typical setup for L2TP deployments, where a PG