Azure VM is not accessible /proc/net/route contains no routes

Problem

Oversudden Azure VMs running Ubuntu 18LTS became unreachable (WestUS region)
/proc/net/route contains no routes


Solution

Connected to Azure VM via Console and got following running lines of error messages

2019/05/30 18:24:20.747552 ERROR ExtHandler /proc/net/route contains no routes

Restart waagent service produced the following:

INFO Daemon Azure Linux Agent Version:2.2.32.2
2019/05/30 18:24:18.242022 INFO Daemon OS: ubuntu 18.04
2019/05/30 18:24:18.246632 INFO Daemon Python: 3.6.7
2019/05/30 18:24:18.251476 INFO Daemon Add daemon process pid 2330 to walinuxagent systemd cgroup
2019/05/30 18:24:18.258645 INFO Daemon CGroups: ok
2019/05/30 18:24:18.263173 INFO Daemon Run daemon
2019/05/30 18:24:18.268142 INFO Daemon Clean protocol
2019/05/30 18:24:18.272685 INFO Daemon Provisioning already completed, skipping.
2019/05/30 18:24:18.277567 INFO Daemon RDMA capabilities are not enabled, skipping
2019/05/30 18:24:18.285862 INFO Daemon Determined Agent WALinuxAgent-2.2.40 to be the latest agent
2019/05/30 18:24:18.613217 INFO ExtHandler Agent WALinuxAgent-2.2.40 is running as the goal state agent
2019/05/30 18:24:18.635339 INFO ExtHandler Detect protocol endpoints
2019/05/30 18:24:18.642625 INFO ExtHandler Clean protocol
2019/05/30 18:24:18.651472 INFO ExtHandler WireServer endpoint is not found. Rerun dhcp handler
2019/05/30 18:24:18.658883 INFO ExtHandler Test for route to 168.63.129.16
2019/05/30 18:24:18.665334 WARNING ExtHandler No route exists to 168.63.129.16
2019/05/30 18:24:18.670932 INFO ExtHandler Checking for dhcp lease cache
2019/05/30 18:24:18.675843 INFO ExtHandler looking for leases in path [/var/lib/dhcp/dhclient.*.leases]
2019/05/30 18:24:18.684096 INFO ExtHandler cached endpoint not found
2019/05/30 18:24:18.690504 INFO ExtHandler Cache exists [False]
2019/05/30 18:24:18.695994 INFO ExtHandler Send dhcp request
2019/05/30 18:24:18.700569 INFO ExtHandler Examine /proc/net/route for primary interface
2019/05/30 18:24:18.705882 ERROR ExtHandler /proc/net/route contains no routes
2019/05/30 18:24:18.710763 WARNING ExtHandler Could not determine primary interface, please ensure /proc/net/route is correct
2019/05/30 18:24:18.717827 WARNING ExtHandler Contents of /proc/net/route:
Iface   Destination     Gateway         Flags   RefCnt  Use     Metric  Mask            MTU     Window  IRTT

2019/05/30 18:24:18.732775 WARNING ExtHandler Primary interface examination will retry silently
2019/05/30 18:24:20.747552 ERROR ExtHandler /proc/net/route contains no routes
2019/05/30 18:24:22.755975 ERROR ExtHandler /proc/net/route contains no routes

VM reboot didn't help, but VM instance stop/start helped.

References
https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/1822133
https://github.com/Azure/WALinuxAgent/issues/980
https://github.com/Azure/WALinuxAgent/issues/1439