By Hugo Strydom, Managing Consultant, Professional Services
I have been asked a few times on what the best option is to load balance with the N1k switch. In this post I want to give an overview of some of the load balancing option that is available on the N1k solution. We will look at different configuration options and when to use which option. From a VMware ESXi host licencing perspective you do need Enterprise Plus on the ESXi hosts that you want to use the N1k vDS.
The N1k supports two types of upstream connectivity namely :
Standard uplinks
Port Channel
With standard uplinks the uplinks are not a member of any PortChannel configuration and provides no load balancing or failover capabilities.
With PortChannel there is two types of PortChannel mechanims to use:
Standard PortChannel
Special PortChannel
Standard PortChannel supports LACP and will act like a Etherchannel. The upstream switches must also be configured with LACP. This type of Portchannel can be configured over multiple physical switches that are part of a cluster. Some of the Cisco family of switches that support clustering is : Nexus 7000 and 5000.
Special PortChannel is used when the upstream physical switches do not support or use clustering. There are two type of configuration options that can be used:
MAC Pinning
vPC Host Mode
With MAC Pinning all the uplinks that have been defined with the N1k VEM will be defined as standalone links and will pin diffents MAC's to the uplinks based on a load balance algorithm. This will ensure that the there is no MAC Flapping on the upstream switches. Advantages of MAC pinning i staht there is not special configuration needed on the upstream switches.
vPC Host Mode will allow you to configure Portchannel on the N1k even if the upstream physicals switches cannot support PortChannel. Thus if a host have 4 pNIC's and 2 is connected to pSwitch A and 2 is connected to pSwitch B, two subgroup PortChannels will be created accross each of the pair's of pNic's that is attached to a pSwitch. Uplinks that connect to the same pSwitch will automaticly be paired into the same subgroup and used the CDP information from the upstream switch for information to create the subgroup PortChannel pairs.
