Dell OptiPlex 980 (Early 2010) - Manual (Page 29)

2. IPv6 Interface ID Type
Under the Wired LAN IPv6 Configuration, select IPv6 Interface ID Type and press Enter.
The auto-configured IPv6 address consists of two parts; the IPv6 Prefix set by the IPv6 router is the first part and the
interface ID is the second part (64 bits each).
Option Description
Random
ID
The IPv6 Interface ID is automatically generated using a random number
as described in RFC 3041. This is the default.
Intel ID The IPv6 Interface ID is automatically generated using the MAC address.
Manual
ID
The IPv6 Interface ID is configured manually. Selecting this type requires
that the Manual Interface ID is set with a valid value.