[systemd-devel] networkd RA being ignored unless promiscous

[Ede Wolf]

Stupid me: For some strange reason I've had Multicast set to no in the 
link section. That should explains everything.
Sometimes, one focuses too long too much on wrong things to see the 
obvious. Probably assuming, when comparing, not having set Multicast at 
all equals "no". I does not.



Am 03.07.24 um 09:46 schrieb Ede Wolf:
> Hello,
> 
> I am having two machines that receive their ipv6 address and their 
> default route via RA, both on the same physikal link, as is the router.
> 
> While one works as expected, the other machine behaves in a way, that it 
> gets it's default route after restarting networkd, but once that has 
> expired, it get's deleted - despite quite a lot RA having been send way 
> beforehand by the router, confirmed with tcpdump (and seen on the other 
> machine as well, where the expire counter gets frequently reset 
> accordingly).
> 
> Wether I am waiting 30 minutes or thee hours, it seems, subsequent RA 
> are completely being ignored.
> Unless, now for the strage part, I set that corresponding interface into 
> promiscous mode.
> Being promiscous, suddenly RA are being honored again, the default route 
> gets reinstalled and the expire timer gets reset with each subsequent RA.
> Removing the promiscous mode and again the route lifetime counts down to 
> zero and gets deleted.
> 
> So in short, expect the inital RA after restarting networkd subsequent 
> RA seem to be ignored unless the interface is in promiscous mode. I've 
> compared the ipv6 sysctl of the interface of the machine that works with 
> that spooky one, no real differences.
> 
> This certainly is not a  general networkd issue, but maybe someone has 
> an idea, what network configuration parameters I might have to recheck. 
> And since restarting networkd does temporarily fix the issue, I've 
> thought, maybe this might be the right place to start.
> 
> Thanks
> 
> Ede