This object defines the mode of source routing
in use on the bridge. If ieee (1) is selected,
explorer frames are modified and the forwarding
path of the specifically routed frames is
determined from the routing information (RI) field.
If passiveBridging (2) is selected, the source
routed frames are bridged across the spanning
tree as if they were transparent frames without
examining or updating the RI field. When in
passiveBridging mode, the same ring number should
be assinged to all active ports of the bridge.