Why mac-pinning preferred over VPC-HM?
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03-02-2012 11:15 AM
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
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Nexus 1000V
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03-02-2012 11:23 AM
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

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03-02-2012 11:30 AM
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
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03-02-2012 12:14 PM
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.

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03-02-2012 12:19 PM
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.
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03-05-2012 11:11 AM
Thanks
Regards,
Brian
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05-31-2012 04:27 AM
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
