I am using RH 9 with kernel 2.4.20-8. I have configured my linux machine to act as a gateway over a PPTP VPN connection. I can ping any machine on the other side of the VPN.

I am trying to use an IP phone over the VPN connection. When the IP Phone boots it tries to get a firmware upgrade from our server using TFTP. I cannot get the TFTP connection to work.

The IP Phone docs provide the following information on port utilization.

Read Request:
[UDP]: IP Phone (Port 1024-5000) <----> TFTP Server (Port 69)

TFTP Data/Acks/Errors:
[UDP]: IP Phone (Port 1024-5000) <----> TFTP Server (OS Selected)

I have gotten this to work with Windows connection sharing, but Windows becomes unstable (shocking).

IP Addresses as follows:
Linux Machine (eth1) : 192.168.4.1
Linux Machine (eth0) : 192.168.2.1
Linux Machine VPN Tunnel (ppp0 -> eth0) : 172.18.19.102
IP Phone : 192.168.4.2

Also, if I bring my laptop up on 192.168.4.2 in place of the phone. I can ping the TFTP server with no problem.

Thanks in advance.