What would cause my IPv6 connectivity to keep dying, with a reboot fixing it each time?

ml flag

Centos 8 Stream

When I first boot my server up, ipv6 works fine. I can ping another ipv6 address without issue.

A few (10?) minutes later, it stops working. Rebooting the box fixes it, but I can't be rebooting a webserver every ten minutes.

Anyone come across this before and have any idea what the issue might be?

I didn't used to have this issue. What's changed is I've had a 10G card added to the server. It now has that and the pre-existing 1G card. I'm only using the 10G card. My /etc/sysconfig/network-scripts/ only has one file, aligning to the card I'm using. Do I need another file for the other card disabling it in some way?

Cockpit tells me that Network Manager Wait Online is failing on every boot - I have a feeling that's ALWAYS been the case, but I can't be certain.

I just tried manually starting that, and it worked, and I lost the ability to ping IPv6 immediately. However the logs show that it's not started under its own steam at all today, so I think that's a red herring.

Any ideas?

Thank you!

A.B avatar
cl flag
IPv6 depends on ICMPv6 for link-layer resolution the same way IPv4 depends on ARP. Could it be you installed custom firewall rules that drop ICMPv6 including those needed for NDP/SLAAC?
Codemonkey avatar
ml flag
After having fought with this issue all day I relented and asked my webhost for assistance, knowing I'd probably have to pay for their time. They replied in minutes, saying "we now have set the ARP-Entries again for your IPs. Please check, if the problem is now resolved.". When I asked if this was something I should have done (and known to do) or if it was something on one of their systems they replied with "The named issue does not seem to be a configuration failure from your site on the first view. If the issue should persist again, we will look into it deeper with you."
Codemonkey avatar
ml flag
Which sounds to me like it was something they screwed up but they don't want to say as much. Very apt that I spent all of Friday 13th fighting an issue that was out of my control without realising it was

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