Hello,

I have a strange issue I have been working on solving off and on for about a year. I have a dial in server connected to a remote site, the purpose of this machine is to dial a modem attached to a piece of equipment. It then dials back to the server and begins transmitting UDP data to my network. Various other machines on my network must receive this data to process it. One way communication is all that is required, the machine sends data only it does not need to receive anything.

The remote equipment's setup cannot be changed. It's IP address is set at 10.50.60.10, and will ONLY send data to 10.60.50.10 the ip of my local dail in server.

So in short I must direct UDP packets coming in on a dial in connection onto a network. The internal network is adapter eth0 and the dail in adapter is ppp0. The packets show up in a tcpdump and are correct. I created an iptables rule to log incoming UDP packets and only see UDP traffic on the eth0 adapter. It seems like these packets from the ppp0 adapter are not being sent to iptables at all.

I have also tried a programs to read data on a socket and retransmit them to other machines on the network. These programs never show received data despite the packets appearing in tcpdump. I have also tried socat with again no results.

Any input on this issue will be helpful.