For fun I'm adding an SNMP server to the IP-stack I wrote (MyIP).

This somewhat works: on a local LAN, I can do a 'walk' (using getnext - no bulk as that is not implemented) without any problems. Over the internet though it often times out after the first exchange (getnext + response), OR completely fails, or works fine - it never fails after e.g. 2 getnext requests. It has been tried on several locations (vps's and isp's).

When I run tcpdump on my firewall, I see packets come in. When I capture them with wireshark, then wireshark says all is fine.

Does anyone have an idea what is wrong with these SNMP packets? example network trace