This week I noticed an issue with no data showing in the Azure Network (Total), Network Out (Sum) and Network In (Sum) tile in the Azure Virtual Machine Overview. I recall noticing this before but couldn’t remember how long ago that was. Looking at other VM’s, most of my them were missing the Network Total information. The only servers that were showing data are virtual firewall appliances.
The first correlation I made was that VM’s not showing overview network data were sending performance data to a Log Analytics Workspace. The ones that showed data in the VM Overview did not have the Azure Monitor Agent installed. I modified the default performance counters, maybe I didn’t have the correct counters added and the tile had nothing to pull from Log Analytics? The Overview Tile only indicates Network In (Sum), Network Out (Sum) and Network (Total). None of these are valid performance counters in Log Analytics. I tried similar counters such as Network Interface and Network Adapter, no luck.
Search results returned little information so I opened a case with Microsoft. Turns out, the Network (Total) and sum for In and Out only show network traffic that is charged by Microsoft. As I mentioned, there is a firewall appliance in this environment that acts as a gateway for all internet and VPN traffic to other sites. Those were reporting traffic because all billable traffic passes through these devices. The Log Analytics correlation I made earlier was just a coincidence.
It’s worth noting that in addition to not showing data, this would cause a deviation in network utilization reported by Azure System and performance data collected by the Azure Management Agent. The first being billable traffic while the second is the actual network traffic for the VM.