Will there be a performance hit on the FWSM with the no monitor session servicemodule command?
A. The span session is required on the FWSM because of a hardware limitation of an ASIC for traffic replication. FWSM needs an ASIC for packet replication and the span session passes the packets to switch for that using the span session. Traffic affected by this command is Distributed EtherChannel, Multicast and GRE. It is recommended to have the span session configured and not to remove it. If for some reason you need to remove it, make sure that you do not have replicated nature traffic, for example, Distributed EtherChannel, that can be affected by the Field Notice: FN – 61935 – Catalyst 6500 Series and 7600 Series Service Module Incompatibility With Distributed EtherChannel and Packet Re-Circulation.
