Three vlans have been assigned to the FWSM i.e. 2 (outside), 3 (DMZ) and 4 (inside).
Now, I would like to perform an inline interface mode monitoring on the traffic coming into FWSM inside interface.
As the FWSM inside interface is logical, how can I configure IDSM to monitor it.
If you have servers 'outside' the FWSM. Just let all the servers be in the same VLAN. And change the VLAN SVI on FWSM from 3 to 33. This way you need to make only one change on the FWSM configuration. Then bridge that in the IDSM. Make sure you allow the correct VLANs on the FWSM internal etherchannel trunk tough (on the Host 6500 Series Switch).
Yes the IDSM will BRIDGE the two vlans, there will be no ROUTING here as both VLANS will be in same subnet
You will assign the sub-inteface 1 you created to the vs0 (virtual sensor). For each new sub-inteface you add (to a physical interface) you need to go and that to the virtual sensor.
Just use the GUI, it will make it all very intuitive.