MATĚJ G‘ÉG‘, TOMÁŠ PODE‘MAŃSKI, MI‘OSLAV ŠVÉDA User identification in IPv6 network 1 USER IDENTIFICATION IN IPV6 NETWORK MATĚJ G‘ÉG‘, TOMÁŠ PODE‘MAŃSKI, MI‘OSLAV ŠVÉDA Users in IPv4 networks typically use only one IP address per interface configured either statically or dynamically via DHCPv4 server. Several techniques can be used to detect violation of that policy. However, IPv6 protocol brings new techniques and possibilities to obtain an IPv6 address. New concepts – autoconfiguration, multiple IPv6 addresses per interface or temporary IPv6 addresses providing privacy for end users introduce new challenges for users identification. Network administrators have to collect additional information for user identification from more sources, e.g. DHCPv6 log, routers neighbor cache, Radius logs, syslog etc. This paper presents analysis of IPv6 address assignment used in current networks together with guidelines how to identify a user in IPv6 networks. IPv6, address assignment, user identification 1. Introduction IPv4 address configuration is mainly based on two methods. Manual address configuration or dynamical configuration via DHCPv4 server. Dynamic configuration via DHCPv4 became the de-facto standard for IPv4 address assignement. Network administrator usually bouŶds users MAC address ;Ŷetǁork-card link-addressͿ to users IPv4 address in DHCPv4 server configuration. The IPv4 address is than assigned by DHCPv4 server to the user with corresponding MAC address. This allows to the administrator to track malevolent users because there is knowledge which IP address belongs to which MAC address and thus the user. This basically means, that the IPv4 address uniquely identify a user. IPv6 (Internet Protocol version 6) is a new version of the fundamental Internet Protocol. IPv6 support is available for all operating systems such as Unix, Mac OS, Windows and usually enabled by default. However, address assignement in IPv6 networks is different. New concepts – autoconfiguration, multiple IPv6 addresses per interface or temporary IPv6 addresses introduce new challenges for users ideŶtifiĐatioŶ. In IPv6 networks, IPv6 address no longer identifies a user. The following sections describe the address configuration process in IPv6 networks and problems connected with user identification.