Hello Shijo,
You can view the link below to configure failover on the two FWSM's. The configuration on the FWSM is independent of whether the switches are configured to operate in VSS mode or not.
http://www.cisco.com/en/US/docs/security/fwsm/fwsm40/configuration/guide/fail_f.html
Both inter and intrachassis models of FWSM failover are supported in VSS mode. The user has to make sure that all VLANs (including failover/state VLANs) are pushed on both failover units (regardless of which physical chassis they reside in). For example, VLAN group N needs to be pushed on switch 1 as well as switch 2 if VLAN group N contains the necessary VLANs (including failover and state).
FWSM failover mode of operations integrates transparently within a VSS environment. One very important aspect is that for both active/standby and active/active, the VSL link needs to have enough capacity to accommodate for "failover" as well as "state" link. It is recommended to plan around 1.5Gbps per pair of FWSM failover units as part of FWSM failover: VSL capacity requirements.You can configure your FWSM's in both active/active or active/standby failover depending on your requirement.
From a logical point of view it is important to note that the VSS chassis will behave as a single chassis, and therefore in this model "autostate + interface monitoring" feature of FWSM will not function even if the two units are spread across the two physical chassis. Remember that this behavior is similar to when both FWSM units reside in the same physical chassis in non-VSS mode (that is, autostate + interface monitoring is not supported).
Regards,
Malavika
