NIC Teaming

[Kahonu84]

Aloha, I'm a bit confused on NIC teaming. When you team two gb adapters, do you have two gb throughput, or is the second NIC strictly for failover??

Mahalo, Bill

[bggb29]

You can use it as failover. Or dpending on the hash algorthym you use you can utilize both nics simultaneosly.

[Kahonu84]

So what you are saying is -

1. If NIC1 dies, NIC2 will do the driving and vice versa?? and

2. Traffic can be balanced between NIC1 and NIC2. However the transfer rate of the team will never exceed 1gb??

Mahalo, Bill

[ServerAdmins]

The VMware document"vmware_virtual_networking_concepts.pdf" explains NIC teaming really well.

As a rough overview, if you only use the ESX teaming, then you'll only get the max throughput for any one VM of the fastest single NIC (ie 1GB).

By default a "route based on source port" method is used by ESX. That means as each VM turns on it uses the next NIC in the team. It stays with that NIC until something fails and it then moves onto another NIC.

Only if you enable "802.3ad Link Aggregation" on the physcial switch side can you get a larger "pipe" than any one NIC.

You may find the following articles helpful:

"Can I combine two etherchannel "pipes" onto one vswitch?" http://communities.vmware.com/thread/143555

"Not clear about Network Failover Configurations" http://communities.vmware.com/thread/144574

Thanks.

[Lee_Sargeant]

My understanding is that the team will run at full speed but a VM will only be able to get a max of 1GB because it will only run from one NIC at a time. Therefore multiple machines will make full use of the available bandwidth. Failover between the cards will happen though should one fail. Hope this helps.

[depping]

Right on Lee. But take STP in consideration. When a nic fails the mac will all of a sudden become active on another physical switch port, with STP in place this will drop all trafic for an X period. For cisco you need to enable Portfast, for other switches you have to turn off STP on the specific ports used by ESX.

Duncan

My virtualisation blog:

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[BenConrad]

'When a nic fails the mac will all of a sudden become active on another physical switch port, with STP in place this will drop all trafic for an X period.'

That is not how it works.

When a NIC failover occurs the remaining failover NIC(s) send out 3 or 4 RARPs in order to update the MAC tables on the network. Since the failover interface(s) is already 'Up' there are no STP actions taking place.

Ben