In my kernel log I found:
lo: 5 rebuilds is over limit, route caching disabled
I know what triggers route cache rebuilds (too long hash bucket chains), but what exactly gets disabled? Which device? How can I check if it is still disabled? How can I re-enable it?
After this strange message I started having problems with other network devices like this:
unregister_netdevice: waiting for TUNNEL_03 to become free. Usage count = 2
And routing cache seems to be guilty here