HP Integrity Virtual Machines Installation, Configuration, and Administration

When VLANs are configured on the vswitch and the guests are required to communicate over
a VLAN with a remote node outside the VM Host, you might need to set up the physical network
appropriately for the VLAN. For information about configuring VLANs on the switches, refer
to the product documentation for the physical network adapters.
If TCP/UDP applications have trouble communicating between a guest and the local VM Host
over a VLAN, it is possible that the host interface for the vswitch is checksum-offload capable.
To resolve the problem, identify the interface used by the vswitch and run the following command
on the VM Host, where 4 is the host interface as shown in the hpvmnet command output.
# lanadmin -X send_cko_off 4
Hardware TCP/UDP (IPv4) transmit checksum offload is currently disabled
8.5 Troubleshooting Network Problems 111