VMWare Standard Vswitch Expected Behavior
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I feel like this is a pretty basic question, but I think I am missing something. Say you have an ESXi box with 2 physical NICs. You provision 2 VMs in the same port group and on the same vSwitch and on the same vlAn. That vSwitch is attached to only one physical server NIC.
In this scenario, my understanding is that for the 2 VMs to communicate via network, the traffic never leaves the ESXi host. Would that still be true if the VMs are contacting one another via DNS nam with the DNS server on a total separate host?
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Suppose you have an application server that is configured to reference a back-end database server by fqdn. I am curious if all traffic stays within the ESXi host. What about if the app server references the database server by ip instead? I would think that would definitely stay within the host but am not sure about the DNS portion (thinking it may actually slow down communication between the VMs).
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DNS itself is only resolution and has nothing to do with the routing or switching of traffic. Resolution traffic would exit the device to hit the DNS server, but the communications itself would behave normally however it would behave if you were manually using IP addresses directly.
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@NetworkNerd said:
Suppose you have an application server that is configured to reference a back-end database server by fqdn. I am curious if all traffic stays within the ESXi host. What about if the app server references the database server by ip instead? I would think that would definitely stay within the host but am not sure about the DNS portion (thinking it may actually slow down communication between the VMs).
FQDN, short name and IP address will all be identical - in all three cases it references by IP Address when it actually does the connection. There is no way at the IP layer (layer 3) to use DNS. DNS is over and done with by that point.
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Reid is dead on. Since it's a vSwitch, no traffic should leave the host as long as the communications are only between those two VMs.
