The PIX, if configured for 'routed' mode, handles intervlan routing by itself while the ASA keeps watch on layer 3 to 7.Ofcourse intervlan routing is not needed for 'transparent' mode. For FWSM the routing is handled by the switch supervisor (MSFC) as the vlans are defined on the sup itself and assigned to FWSM.To enable intervlan routing the administrator will ofcourse have to configure policies(ACLs) to allow traffic to be routed as the default ASA behaviour would not allow traffic between different security regions.
