Hello Brian. vPC-HM (host mode) is how the Nexus 1000v does the port-channeling. With this vPC-HM there are 3 options on how the port-channeling is done. This is configured on the port-profile of type "Ethernet" that is used by the physical NICs on your ESX/ESXi servers. The command used for this is:
channel-group auto mode active | passive| on [mac-pinning or cdp]
- mac-pinning
- load-balances the available links (i.e. port-channel) based upon mac-address of the VM. So VM1 will flow through say vmnic0 and VM2 will flow through vmnic1, where vmnic0 and vmnic1 is this vPC-HM port-channel. If vmnic0 fails, then all VM traffic will start to flow on vmnic1 as normal HA.
- cdp
- This is load-balanced based up the Cisco Discovery Protocol (cdp) on the upstream switch. This is typically not used and is not recommended.
- lacp {active | passive}
- Link Aggregation Control Protocol (lacp) provides a better hashing algorithm to load-balance on the available uplinks in that port-channel providing better utlization of the links and allows that VM to use all availalbe links.
- lacp can be used if all interfaces are connected to the same physical upstream switch
- if the uplink interfaces are connected to 2 separate physical upstream switches, then a Multi-Chassis EtherChannel technology needs to be available on those upstream switches for lacp to be used. Example of Cisco switches that has this capabilities are all Nexus 7K, 5K/2K using vPC. Cisco Catlayst 6K using VSS or Catalyst 3700 using stacking.
With the UCS blades interfaces pinned to a particular FI (i.e. vnic0 to Fabric-A and vnic1 to Fabric-B) and since the FI are not capable to have vPC for the blade servers, that leaves the option of either mac-pinning or cdp. Since mac-pinning is the recommended between the 2 options, that is why you see all deployments of UCS with N1KV today using mac-pinning. Hope this helps.
Cuong
