Monday, 1 June 2015

Troubleshooting poor network performance with ESXITOP

When networking issues arise a good place to start is ESXTOP:

SSH into the ESXI host >> esxtop >> press 'n'.

This will present you will all of your ports, network labels, vSwitch names and so on. The significant columns here are '%DRPTX' and '%DRPRX' - hence indicating that the vSwitch queue has been exhausted and packets are being dropped.

The other columns are reperesented as follows:

- MbTX/s: Data transmitted in mbps.
- MbRX/s: Data recieved in mbps.
- PKTTX/s: Average number of packets transmitted per second
- PKTRX/s: Average number of packets recieved per second

Possible causes could be:

- High guest CPU utilization
- Insufficient bandwidth supplied by the uplink

Possible resolutions include:

- Network I/O control
- Moving network hungry VM's onto another host
- Upgrading the uplink capacity

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