Information Technology Reference
In-Depth Information
Because a vSwitch cannot be used in any way without at least one port or port group, you'll
see that the vSphere Web Client combines the creation of new vSwitches with the creation of
new ports or port groups.
As shown in Figure 5.2, though, ports and port groups are only part of the overall solution.
The uplinks are the other part of the solution that you need to consider because they provide
external network connectivity to the vSwitches.
Understanding Uplinks
Although a vSwitch allows communication between VMs connected to the vSwitch, it cannot
communicate with the physical network without uplinks. Just as a physical switch must be con-
nected to other switches to communicate across the network, vSwitches must be connected to
the ESXi host's physical NICs as uplinks to communicate with the rest of the network.
Unlike ports and port groups, uplinks aren't required for a vSwitch to function. Physical sys-
tems connected to an isolated physical switch with no uplinks to other physical switches in the
network can still communicate with each other—just not with any other systems that are not con-
nected to the same isolated switch. Similarly, VMs connected to a vSwitch without any uplinks
can communicate with each other but not with VMs on other vSwitches or physical systems.
This sort of coni guration is known as an
internal
-
only
vSwitch. It can be useful to allow VMs to
communicate only with each other. VMs that communicate through an internal-only vSwitch do
not pass any trafi c through a physical adapter on the ESXi host. As shown in Figure 5.5, commu-
nication between VMs connected to an internal-only vSwitch takes place entirely in the software
and happens at the speed at which the VMkernel can perform the task, whatever that may be.
Figure 5.5
VMs communi-
cating through
an internal-only
vSwitch do not pass
any tra
c through
a physical adapter.
ESXi host
Internal-only
vSwitch
vSwitch0
vmnic0
vmnic1
vmnic2
vmnic3
No Uplink, No vMotion
VMs connected to an internal-only vSwitch are not vMotion capable. However, if the VM is dis-
connected from the internal-only vSwitch, a warning will be provided, but vMotion will succeed
if all other requirements have been met. h e requirements for vMotion are covered in Chapter 12,
“Balancing Resource Utilization.”
