Connecting to a Redundant Switch System
You can include multiple interfaces per threat defense in the Spanned EtherChannel. Multiple interfaces per threat defense are especially useful for connecting to both switches in a VSS, vPC, StackWise, or StackWise Virtual system.
Depending on your switches, you can configure up to 32 active links in the spanned EtherChannel. This feature requires both switches in the vPC to support EtherChannels with 16 active links each (for example the Cisco Nexus 7000 with F2-Series 10 Gigabit Ethernet Module).
For switches that support 8 active links in the EtherChannel, you can configure up to 16 active links in the spanned EtherChannel when connecting to two switches in a redundant system.
The following figure shows a 16-active-link spanned EtherChannel in a 4-node cluster and an 8-node cluster.