Debugging a multicast ntp server today. I want to see if it's throwing the right IGMP packets, and if it will finally throw those damned NTP multicast packets.

tcpdump comes to the rescue, and it turns out that ntpd is not doing what it's supposed to do, so I am in for further debugging and research 😦

By the way, the tcpdump line I used is:

tcpdump '( (ip multicast) and (dst port ntp) ) or igmp '

PS: forgot to say: that's a Debian Lenny system.