The network panel in ESXTOP has a few metrics that will enable you to determine issues such as loss of network on a VM or high dropped packet on specific nics. Below is simple overview on how to use esxtop for networking:
How to access:
Log into your ESXi host and type esxtop
Press ‘n’ to show only the networking view
Port ID - The port ID used on the virtual switch. This ID is used for example for network traces with pktcap-uw.
Press 'N' to sort by PORT-ID column.
USED-BY - Indicates what is connected to the virtual switch port. Connected devices can be virtual machine NICs, VMkernel ports (vmk#), physical NICs (vmnic#) or ports used for health checks (Shadow of vmnic#).
TEAM-PNIC - The physical NIC that the corresponding device is actively using. This information is helpful for network troubleshooting.
%DRPTX - Dropped packets transmitted, hardware overworked. Possible cause : very high network utilization.
%DRPRX - Dropped packets received, hardware overworked. Possible cause : very high network utilization.
ESXTOP can provide live view of the physical network showing us the MbTX/s and MbRX/s (Amount of data transmitted or Received in Mbps) on each of the virtual switch of the ESXi host.
In problem-solving, recognizing the bottleneck or the Root case always becomes critical and hence the parameter of dropped packets becomes important.
Dropped packets can occur for a number of reasons. Possible causes include
high guest CPU utilization,
having incorrect network drivers installed in the guest OS.
insufficient uplink capacity in the vSwitch to cope with demand.
Some other metrics shown are
MbTX/s – Amount of data transmitted in Mbps
MbRX/s – Amount of data received in Mbps
PKTTX/s – Average number of packets transmitted per second in the sampling interval
PKTRX/s – Average number of packets received per second in the sampling interval
Some great resources for learning ESXTOP:
Gather esxtop using cronjob - https://kb.vmware.com/s/article/1033346