[CentOS] After upgrade to CentOS 8.1 default gateway missing

Thu Jan 16 14:34:43 UTC 2020
Stephen John Smoogen <smooge at gmail.com>

On Thu, 16 Jan 2020 at 07:58, Asle Ommundsen <aommundsen at gmail.com> wrote:
> Hi,
> Tonight I upgraded two CentOS 8 boxes to CentOS 8.1 (1911). Then after a
> reboot of the first server the network was unavailable. In IPMI console
> everything except the network was looking good. Network was unreachable.
> No errors in NetworkManager. I also restarted NetworkManager, but it did
> not help. Then I discovered that the default gateway suddenly was missing.
> Then I rebooted the server one more time, but network was still down.
> Then both myself and a technician in my datcenter was debugging this (I
> had to wake him up in the middle of the night, costing me a lot of money),
> without finding any reason for why the default gateway was missing after
> reboot.
> Then we rebooted the server a third time, and all of a sudden the problem
> was gone and the default gateway was back.
> Then, after this, I also upgraded my second CentOS 8 server to CentOS 8.1
> and did a reboot. And the very same thing happened to this server after
> reboot! The default gateway was missing after reboot, and network was
> down. Then I did a extra reboot of this server also, and when it came back
> up everything was working correct and the default gateway was back.
> So the first server I needed to reboot two extra times to have the default
> gateway back and network working. And the second server I needed to reboot
> only one extra time for the problem to be solved.
> The two boxes is not VPSs or anything, but bare metal dedicated servers.
> Also prior to upgrading to CentOS 8.1, these two boxes has been rebooted
> serveral times previously, without any problems at all. Only after
> upgrading to CentOS 8.1 this happened on both of them for the first time.
> I can't believe I am the only one that experience this? My guess is that
> this is a unknown random intermittent bug in CentOS 8.1 that kicked in. I
> just hope this does not continue to happen in the future. If you
> experienced the same, please share it with a reply. Thank you!

In order to determine what is going on you need to give a lot more information.

1. How do these boxes get their network information? DHCP or static
2. If they are static, what controls the setting of ips:
NetworkManager or network-scripts
3. If they are static, how are they set in /etc/sysconfig/network-scripts/
4. Do the files in /etc/sysconfig/network-scripts list a GATEWAY=
5. If you are using network-manager, what does nmtui or the graphical
tool say the gateway or default route is?

> Kind regards,
> Asle Ommundsen
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Stephen J Smoogen.