VMS Help LANCP, SET, DEVICE parameters, Qualifiers, /AGING_TIMER  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /AGING_TIMER=value

    Sets the amount of time in seconds to age Token Ring source
    routing cache entries before marking them stale. This timer
    expires when no traffic is sent to or received from the remote
    node in this amount of time. The default value is 60 seconds.

    Increase this value when idle connections bounce between the
    stale and known states. Setting this value too low may cause
    unnecessary explorer traffic to traverse the LAN.