![]() OS clones are likely to have identical DUIDs. This characteristic of DHCPv6 DUIDs has caused some interesting challenges given the popularity of cloned and/or virtual OSes. For instance, when I reboot my host I wouldn’t want to have a new DUID each time. ![]() Of course for the DUID to provide such identification it should be stable for any given host. DHCP clients use DUIDs to identify a server in messages where a server needs to be identified.” The main idea behind a DUID is to provide a way to unambiguously identify all hosts (including the DHCPv6 server itself) rather than single interfaces on any host.Īccording to RFC 3315, Dynamic Host Configuration Protocol for IPv6 (DHCPv6): “DHCP servers use DUIDs to identify clients for the selection of configuration parameters and in the association of IAs with clients. Instead of a MAC address to identify clients, DHCPv6 utilizes something called a DHCP Unique Identifier (DUID). The untranslated MAC address is 00:0c:29:7e:59:e7.įigure 2 shows the MAC address on the host that originated it.Ĭonfiguring a fixed host address (AKA a static reservation) in IPv4 DHCP using the MAC address is so trivial we could be excused for assuming that DHCPv6 makes it just as easy. It shows a value of Vmware_7e:59:e7, where Wireshark is kind enough to substitute VMware for its OUI of 00:0c:29. The second highlighted-in-orange line is the Client MAC address field. This provides unambiguous identification of a host machine (or, more accurately, a particular interface on a host machine) and has been used for years in network operations to help facilitate everything from configuring fixed addresses in DHCP to provisioning processes, asset tracking, security policy enforcement.įigure 1 shows a packet capture of a DHCP Discover sent from a virtual instance of Ubuntu Linux running on the same segment during its interface initialization.įigure 1: DHCP Discover packet with included Client MAC address highlighted By Tom Coffeen, Chief IPv6 Evangelist, InfobloxĭHCP in IPv4 has a taken-for-granted characteristic that provides it with powerful management flexibility: If you pull apart a DHCP header you find the MAC address of the host that originated the packet.
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