RMC inactive for RHEL 8.0 guest OS on NovaLink hosts

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Problem

IPv6 interface fluctuates when managed by NetworkManager with IPV6_AUTOCONF=yes.

Explanation

When IPV6_AUTOCONF=yes, router advertisement is enabled for the IPv6 interface, which internally engages IPv6 router. Here, IPv6 interface is used to establish communication between NovaLink and guest OS. When there is no router, NetworkManager continuously activates and deactivates network, which results in fluctuation of IP address.

These fluctuations interrupt communication between NovaLink and guest OS causing RMC state to toggle between active and inactive.

Resolution

Perform the following steps to troubleshoot this issue.
  • For new virtual machines:
    • Remove refresh_rmc_and_interface in the cloud_final_modules section of /etc/cloud/cloud.cfg.
    • Add bootcmd instruction at the end of /etc/cloud/cloud.cfg file 
      bootcmd:
- 'echo "IPV6_AUTOCONF=no" >> /etc/sysconfig/network-scripts/ifcfg-$(ls  /sys/class/net -1| grep env.|sort -n -r|head -1)'
    • Deploy virtual machine by using the new image.
  • For existing virtual machines:
    • Add the NM_CONTROLLED=yes and IPV6_AUTOCONF=no entry in the /etc/sysconfig/network-script/ifcfg-* file for the IPv6 interface identified.
    • Run this following command after making necessary changes.
      # nmcli connection reload