>> >> Maybe run a ping to a destination which you are having problems
>> >> with, then reproduce the problem (with the network idle
>> >> otherwise). You should see ping packets dropped only then.
>> >> You can also ping with increasing packet sizes (see ping --help)
>> >> and see when the packet becomes too big for path MTU. But instead
>> >> lowering your MTU then, you should allow icmp-fragmentation-needed
>> >> come through reliably. Lowering MTU only makes sense to stop
>> >> overly fragmentation in the first place and optimize for a
>> >> specific packet path (like traffic through one or multiple VPN
>> >> tunnels) where fragmentation would otherwise increase latency a
>> >> lot, or where icmp-frag-needed does not correctly work.
>> > I'll try pinging today once the issue pops up.
>> I'm seeing the issue again as usual but ping response times come back
>> normal at about 50ms. I'll keep trying.
> Not sure if this came after or before switching your router to modem
> mode... But if it happened before and is solved now, your router really
> doesn't well with icmp packets or has problems with mss clamping / pmtu.
I did not try pinging before switching the device from router to modem.
BTW, I read that setting CLAMPMSS=Yes in shorewall.conf is a necessity
when using PPPoE but my connection is working fine without that
setting. Should I set it anyway?