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Why mac-pinning preferred over VPC-HM?

Afilias Canada
Level 1
Level 1

Hi,

For uplink port channels in 1000v, I am seeing mac-pinning chosen in many best practice guides when used in Cisco UCS.  However, I have not been able to find any documentation why mac-pinning is infact better choice than VPC-HM for deploying 1000v within VMware vSphere on UCS.

Can someone enlighten me on this?

Thanks.

Brian

6 Replies 6

Robert Burns
Cisco Employee
Cisco Employee

Mac-pinning is a form of VPC-HM.

Since UCS doesn't support host-based port channels (yet), the only other option is mac pinning.  Mac pinning is simple and solid.  I recommend MAC pinning to most people unless they severly requires the aggregate bandwidth of a port channel - assuming the Host can support it.

Regards,

Robert

cutran
Cisco Employee
Cisco Employee

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]

  1. 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.
  2. 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.
  3. 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

Thank you guys.  I am trying to see why cdp approach is not recommended.  Is there anything that makes it undesirable?   I understand this would require a CDP enabled switch and thus not an option when you don't have cdp enabled upstream switch.  

Thanks again.

As Robert commented, it's quite simple and pretty solid.  CDP does the exact same thing as mac-pinning but again, based upon mac-address vs. upstream switch using cdp.  Since not everyone has CDP, mac-pinning is preferred to make things simpler and has a lot more solid track right now.

Thanks

Regards,

Brian

fbcasero62
Level 1
Level 1

hello,

can i configure mac pinning and static pinning together?

In lab we have configured vPC-HM with static pinning to force the fabric used for a service and it works ok, but static pinning does not work in lab with mac pinning..

Regards

Francisco

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