No ICMP Replys with NAT unter Win2k3 SR2

Hello,

I'm new to this newsgroups. First, excuse for my bad english.

I've a scenario like this:

________ ______ ____________
| | | | PPP- |Client |
| Client |----- |Server|----------------|in private |
|________| |______| Connection |_LAN_____|
172.16.1.1 172.16.1.2 (RS232)
NAT - 172.16.1.40

The Server in the Middle sets up a PPP Connection with an RS232 Cable on
COM1. The Server gets on the PPP Interface the IP-Address 192.168.1.2. The
Client on the right side himselfs get the 192.168.1.1.

Now, the Client on the left side must access the Client on right side per
telnet. He request the 172.16.1.40, thats the ip, that will be forwarded
(NAT) on the server to 192.168.1.1, so that the client on left side gets
access to the client on the right side. that works quite well, but only with
telnet.

if the client on the left side pings the 172.16.1.40 he doesn't get a ping
reply from the client on the right side? where is the problem ? i've
activated all icmp checkboxes in the nat settings, and i'm confused, that
telnet already works.. but icmp not.

is there a problem with ICMP on the server, that windows cant forward icmp
packets?

dos anyone have an idea whats the problem in these scenario ?

greets,

christian