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IDProjectCategoryView StatusLast Update
0018556CentOS CIgeneralpublic2023-01-07 21:08
Reporteragoodm Assigned To 
PrioritynormalSeveritymajorReproducibilityrandom
Status assignedResolutionopen 
Platformx86_64OSCentos StreamOS VersionRelease 8
Summary0018556: IPv6 traffic sometimes does not pass on vlan tag interface unless interface is in promiscuous mode
DescriptionMy company builds bespoke PC based routers. Currently these are all based on Centos 7 however I am attempting to port this to CentOS Stream 8.

Typically I am using RP-PPPOE, widedhcpv6 bind dhcpd iptables tc etc.

Topology is typically an internet connection -> PC based router -> VLAN tag interfaces -> switches/access points -> clients.

Nics are mostly Intel NICs using igb driver.

On my test network I've been investigating unusual performance degradation impacting Android and iOS devices. I've found that IPv6 connectivity is intermittently failing for impacted wired/wireless devices; this is presumably causing the weird delays I perceive when using my mobile phone (yes I also tested with hard wired android devices). I've not been able to replicate the fault using wired/wireless Windows/Linux desktop devices.

During my testing I would wait for an android or iOS device to get into the broken state, I would then start a pcap on various network devices and immediately find that the issue had gone away. I spent *many* hours checking firewall rules, updating software, firmware, resetting devices, various settings all manner of different things. Eventually I reverted all my tweaks and placed the interface into promiscuous mode and found that the fault did not recur.

I spent ages trying to think about any filtering 'above' the firewall which might be disabled in promisc mode and cant think of anything. Therefore I have settled on this likely being a kernel bug or something 'weird'. Any input would be appreciated?
Steps To ReproduceTricky, but the summary is set up a router with IPv6 routing and VLAN tag interfaces on at least one side.

Random googling suggests that this issue might occur by simply attempting to use IPv6 on a VLAN interface.
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Issue History

Date Modified Username Field Change
2023-01-07 21:08 agoodm New Issue
2023-01-07 21:08 agoodm Status new => assigned