Hello Alan, Thanks for your reply. I know that icmp is being handled by the router's cpu and that the forwarding is being done in hardware. The interesting part here is that the loss starts at the router where the asynchronous routing begins and is even being seen at the final destination host - but this only happens with pathping and mtr. An ordinary ping doesn't show this problem. The problems in mtr/pathping disappear when a synchronous routing is being established. What's the case for this? What are the programmers of mtr and pathping doing wrong or is there another problem mayb in the implementation of icmp? Gunther

-----Ursprüngliche Nachricht----- Von: Alan Clegg [mailto:alan@clegg.com] Gesendet: Dienstag, 6. Juni 2006 17:27 An: Gunther Stammwitz Betreff: Re: Phantom packet loss is being shown when using pathping in connection with asynchronous routing - although there is no real loss. [..]

I'd guess that the routing devices are just droping/ignoring ICMP echo request packets. They are the least interesting packet, and are quite often, responses to them are given extremely low priority.

Just my guess, AlanC