6.7

Table Of Contents
The VMware Host Client uses port 902 to provide a connection for guest operating system MKS activities
on virtual machines. It is through this port that users interact with the guest operating systems and
applications of the virtual machine. VMware does not support configuring a different port for this function.
Secure the Physical Switch
Secure the physical switch on each ESXi host to prevent attackers from gaining access to the host and its
virtual machines.
For best protection of your hosts, ensure that physical switch ports are configured with spanning tree
disabled and ensure that the non-negotiate option is configured for trunk links between external physical
switches and virtual switches in Virtual Switch Tagging (VST) mode.
Procedure
1 Log in to the physical switch and ensure that spanning tree protocol is disabled or that Port Fast is
configured for all physical switch ports that are connected to ESXi hosts.
2 For virtual machines that perform bridging or routing, check periodically that the first upstream
physical switch port is configured with BPDU Guard and Port Fast disabled and with spanning tree
protocol enabled.
In vSphere 5.1 and later, to prevent the physical switch from potential Denial of Service (DoS)
attacks, you can turn on the guest BPDU filter on the ESXi hosts.
3 Log in to the physical switch and ensure that Dynamic Trunking Protocol (DTP) is not enabled on the
physical switch ports that are connected to the ESXi hosts.
4 Routinely check physical switch ports to ensure that they are properly configured as trunk ports if
connected to virtual switch VLAN trunking ports.
Securing Standard Switch Ports with Security Policies
The VMkernel port group or virtual machine port group on a standard switch has a configurable security
policy. The security policy determines how strongly you enforce protection against impersonation and
interception attacks on VMs.
Just like physical network adapters, virtual machine network adapters can impersonate another VM.
Impersonation is a security risk.
n
A VM can send frames that appear to be from a different machine so that it can receive network
frames that are intended for that machine.
n
A virtual machine network adapter can be configured so that it receives frames targeted for other
machines
When you add a VMkernel port group or virtual machine port group to a standard switch, ESXi configures
a security policy for the ports in the group. You can use this security policy to ensure that the host
prevents the guest operating systems of its VMs from impersonating other machines on the network. The
guest operating system that might attempt impersonation does not detect that the impersonation was
prevented.
vSphere Security
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