ple, if DHCPv6 would always provide the same IPv6 address for a node, tracking is made easier as long as the node stays within a network. To avoid problems with static addresses, DHCPv6 supports allocation of both Temporary Addresses (DHCPv6 option) and Non-temporary Addresses (DHCPv6 IA_NA) option. A node wishing to increase privacy would prefer using temporary addresses over non-temporary addresses. In addition to the abovementioned solutions, implementations may sometimes use other approaches. These include randomizing IID when connecting to a network, but not chang- ing the IID during the lifetime of a network connection. This fully solves the problem of tracking host movement through different access points, and also within a network as long as network connection lifetime is not excessively long. In some other scenarios, like 3GPP, the IID may also be received via layer 2, in which case the responsibility of avoiding static IIDs is left for the layer 2 implementation (for the network entity providing the IID to a host). 3.5.6 Router Selection Internet hosts are sometimes connected to networks that have more than one first-hop router, and sometimes the hosts are simultaneously connected to multiple networks. Deploying IPv6 in 3GPP Networks Multiple routers can be present on one link, for example, in order to provide redundancy or to provide access to different networks - such as the Internet and a private network. Hosts will configure IPv6 addresses from all prefixes they receive advertisements for, indepen- dent whether they originated from one or more routers. From the multitude of configured addresses, hosts choose the address to use based on source address selection algorithms. However, when a host is sending packets, it needs to determine which router to send the packets. Note that a host is not mandated to keep track which router advertised each prefix, which may cause issues (see Section 3.5.4). A tool for improved router selection is defined in RFC 4191, 'Default Router Preferences and More-Specific R