No ICMP connections in /proc/net/ip_conntrack?

[Asim Shankar <asimshankar@gmail.com>]

Hi,

I can't see any ICMP entries in /proc/net/ip_conntrack. My setup is as follows:

Machine A: 
- Connected to the internet on eth0 and to a private (192.168.1.0/24) on eth1.
- iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

Machines B and C:
- Connected to the private (192.168.1.0/24) network on eth0
- Default gateway: Machine A

Machine D:
- Connected to the internet

If I ssh/ftp/run a udp-echo client on machines A/B, connecting to
machine D, I can see the entries in /proc/net/ip_conntrack on machine
A.

However, if I "ping D" from A and B, then no entry seems to be present
in ip_conntrack. My understanding based on:
http://www.faqs.org/docs/iptables/icmpconnections.html is that I
should see something in ip_conntrack.

Am I missing something?

Thanks,
Regards,

-- Asim