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Dave_Whitla_254's avatar
Dave_Whitla_254
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Nov 25, 2011

VE cannot establish TCP connections from VLAN interfaces to other guests on untagged ports of the same VLAN

I've just spent a couple of days scratching my head on this one. I may just be slow, but in any case, to spare others the pain, here's the solution.       First the problem.   ...
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virtualization
Dave_Whitla_254's avatar
Dave_Whitla_254
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Dec 01, 2011
I haven't actually tested this on Citrix XenServer, but AFAIK the code in question is identical to that on OS Xen.

 

So I expect identical behaviour on XenServer to that which I have described. Incidentally the hypervisor doesn't tag anything, the dom0 kernel does. As described, the problem occurs when you must mix trunked and untagged ports on the same host.

 

 

As for virtual hardware tx offload - I doubt it would be a performance improvement as the LTM vm is fully virtualised not paravirtualised. As a result the "virtual hardware" runs in host user-space where you're looking at 8 context switches for every guest IO.

 

 

* context-switch to guest kernel

 

* context-switch to hypervisor

 

* context-switch to dom0 kernel

 

* context-switch to dom0 qemu-dm

 

* context-switch to dom0 kernel

 

* context-switch to hypervisor

 

* context-switch to guest kernel

 

* context-switch to guest application

 

 

If F5 used the pvops kernel and the PV xennet drivers there might be some performance improvement.

 

 

Dave