We received a question from a customer asking about support for a feature called Asynchronous Port Channel and if it was supported in the GA code.
virtual Port Channel Host Mode (vPC-HM), which was known as Asynchronous Port Channel during the Nexus 1000V Beta testing, is fully supported in the GA code.
Most access layer switches do not support clustering technology, yet most Cisco Nexus 1000V Series designs require PortChannels to span multiple switches. To enable this spanning of switches, one can use a PortChannel in vPC-HM. vPC-HM divides the PortChannel into subgroups, with each subgroup representing one or more uplinks to one upstream physical switch.
Note When using virtual PortChannel – Host Mode the Cisco Nexus 1000V Series only supports two subgroups, 0 and 1.
Links within the PortChannel that are connected to the same physical switch are bundled in the same subgroup automatically by using the Cisco Discovery Protocol (CDP) packets received from the upstream switch. Alternatively interfaces can be manually assigned a specific subgroup using interface level
configuration.
When using vPC-HM each vEth interface on the VEM is mapped to one of the two subgroups using a round-robin mechanism. All traffic from the vEth leverages the assigned subgroup unless the assigned subgroup is unavailable, at which point the vEth will failover to the remaining subgroup. Once the
originally assigned subgroup becomes available again traffic will shift back to its original location. Traffic from each vEth is then hashed within its assigned subgroup based on the configured hashing algorithm. vPC-HM should be considered the preferred method for most Cisco Nexus 1000V Series deployments.
Hope this helps,
pf
