TL;DR To route VM-a traffic off the host to VM-b on another host, a p-NIC must be associated with the DVswitch attached to a DPG. Sorry, its a simple question now that I write it... but it might help someone else in the future.
I have a scenario where traffic wont route except for when the two VM's are on the same host.
Even if the VMs are on the same, VLAN, DPG and vSwitch.
I think I know why but I want another opinion!
This scenario is a number of VMs on a single distributed port group "DPGa", Attached to "DvSwitch-a" without any up-links or p-switching. That may tell you enough already.
Of these VMs, two (a firewall and a Linux box) VMfire and VMLinux both have a second NIC and use it to attach to "DPGb", which is on a "DvSwitchb" and this has p-up-links to a p-switch.
3 hosts total and not much else going on, simple setup.
When VMLinux is on a different host, it cannot see VMfire at all.
It can see the outside world through DPGb
If VMLinux is v-motioned onto the same host as other VMs, it can see VMfire.
My understanding is that Dvswitches and DPGs, without a physical switch backing and up-links, cannot route traffic off-Host at all?
Which now that I say it... how else would it work, right?
This particular scenario only needs local traffic, I didn't recognise the need for physical switching as I considered a DvSwitch to be magic....
So the question then is, why does vSphere let you join a VM to a DPG when it cannot route traffic into the DPG, there is no warning on that?
Message was edited by: G M. Last line question
