802.1Q trunking from VMware ESX3 server

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Mar 28th, 2007
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Hi All,


I have been asked to enable 802.1q trunking from our core switches to a VmWare ESX server. The server does not support spanning-tree protocol and they recommend turning off spanning-tree all together or using portfast on the trunks. The server manufacturer says that loops are not formed; but I am not finding any info on how they do not form loops if they do not use spanning-tree.


Has anyone around here seen this sort of thing before?


many thanks





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mmarlowe Wed, 03/28/2007 - 10:05
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First of all, unless you really are using alot of vlans on the ESX boxes, its typically better to just put additional network cards as that will also improve vmware performance. It is not that unusual to have 2-3 NICS assigned to each virtual switch. Using VLAN's is more efficient from a network engineering perspective, but vmware systems are meant to use heavy duty hardware and I frequently see systems configured with 8 NIC ports + FiberChannel or iSCSI.


Certainly from a network engineer perspective, this seems to be highly inefficient and thats where the request for 802.1q trunking usually comes in. I believe vmware's reference to loops is really w/ regard to their own virtual switches. Since virtual switches dont connect between each other and virtual machines have their nics virtualized so that there is only one/vlan per vm, there really isnt any way for loops to form inside vmware. That said, I would not turn it off on physical switches. Just use portfast.

bgleason Fri, 04/20/2007 - 11:32
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We run trunks into our esx 2.5 and 3.01 servers.

Vmware clearly states they cannot create a brdige loop.

We running spanning tree portfast on the trunks.


No problems.


There is a whitepaper on the vmware site, as well as ppt presentations from vmworld 2006. Search the vmware esx 3.0 forums on the vmware site

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