This read-write enumerated integer selects the bridge's default action for a frame that fails to match any entry in the Generic special database: filter, forward, or searchFDB to fall back to the standard IEEE 802.1D transparent filtering database. An administrator sets this to define the fallback disposition for traffic on media types covered by the generic filter mechanism when no explicit rule applies. For example, on a mixed-media bridge, an admin sets this to searchFDB(3) so unmatched generic-database frames are still subject to normal learned-address forwarding rather than being dropped outright.