One of my customers experienced high CPU load on their physical switch. After some investigation they noticed broadcasts packets being sent every two seconds. The first reaction was Beacon Probing is probably enabled.
Unfortunately this wasn’t the case. But VMware GSS came to the rescue and pointed us towards a KB article. Apparently a bug has been identified in 4.0 which causes this behaviour:
src: http://kb.vmware.com/kb/1024435
Problem:
- ESX sends Beacon Packets when vDS/vSwitch are connected to more than one uplink.
- ESX server sends periodic broadcast of Beacon Packets even if the vSwitch/vNetwork Distributed Switch (vDS) is not configured to use Beacon Probing for Network Failover Detection.
- These packets have the virtual MAC of the vmnic in the Source MAC Address field.
Workaround:
#esxcfg-advcfg -s 0 /Net/MaxBeaconsAtOnce
The customer implemented this workaround and the problem is gone… From what I have been told this issue does not exist in ESX(i) 4.1 so if you are experiencing it, an upgrade might be a better solution. In this case due to the size of the environment that was not an option.
Justin Paul says
Does this normally only affect customers with a large number of ESX hosts? our normal install is 2-5 hosts … should i be looking for this ?
Thanks Duncan!
Duncan Epping says
No probably not. But I would recommend looking at your physical switch to see if it is highly utilized or not, if its not forget about it 🙂