How much bandwidth does failover require?
A. There are 2 aspects to it. One is the amount of bandwidth required for data traffic. The trunk between the 2 6500s should be capable of carrying as much traffic as is presently going through the active FWSM, in case a failover happens. The documentation recommends 6Gbps because the max forwarding capacity of the FWSM in terms of bandwidth is 5.5Gbps (close to 6Gbps). You do not necessarily need 6Gbps of course. The second aspect is the bandwidth required by the failover protocol itself (the failover LAN interface). This depends on the number of connections per second going through the box. At a rate of 100K new CPS, the failover protocol takes up 670Mbps. It is safe to assign a 1Gbps link to the failover state VLAN.
