The Free On-line Dictionary of Computing (30 December 2018):

dual-attached

   The form of FDDI interface where a device is connected to
   both FDDI token-passing rings, so that uninterrupted operation
   continues in the event of a failure of either of the rings.
   All connections to the main FDDI rings are dual-attached.
   Typically, a small number of critical infrastructure devices
   such as routers and concentrators are dual-attached,
   whereas host computers are normally single-attached or
   dual-homed to a router or concentrator.

   For example, a ring could be formed between a single router
   and two concentrators (all dual-attached) then all other
   components that need to be fault-tolerant (typically file
   servers) can be dual-homed to both concentrators.

   (1994-12-13)