udp packet on port 111

["Massimo Balestra" <m.balestra@reply.it>]

Hi everybody,

I have problem with iptables and maybe somebody can help me to find a
solution.

I need to connect to another network through a ppp connection.

What I did has been: to set the ppp connection and set iptables to forward
the packets with the remote network as destination to the ppp.
Then I set the route of my pc using the linux machine as the gateway.

Everything works well, http, ssh, xwindows, is all OK. I can also enter into
a Cisco VPN in the remote network.
There is only one application that does not work.

I don't know how this application is done. I simply did a tcpdump while I
was using this application.
Note: the ping from my pc to the destination server works. Only this
application doesn't. Unfortunately it is a windows application. Looks that
this application receives and sends udp packets but they are not forwarded
correctly.

Here is the tcpdump / windump result. (sunrpc is port 111)

------------------------------
on the gateway machine:
tcpdump -i ppp0

15:02:30.528227 10.5.17.21.1491 > 10.21.109.84.sunrpc:  udp 56
15:02:30.675801 10.21.109.46.sunrpc > 10.5.17.21.1491:  udp 28 (DF)
15:02:30.675840 10.5.17.21 > 10.21.109.46: icmp: 10.5.17.21 udp port 1491
unreachable [tos 0xc0]
15:02:45.530046 10.5.17.21.1491 > 10.21.109.84.sunrpc:  udp 56
15:02:45.728534 10.21.109.46.sunrpc > 10.5.17.21.1491:  udp 28 (DF)
15:02:45.728564 10.5.17.21 > 10.21.109.46: icmp: 10.5.17.21 udp port 1491
unreachable [tos 0xc0]
15:03:15.548364 10.5.17.21.1491 > 10.21.109.84.sunrpc:  udp 56
15:03:15.683612 10.21.109.46.sunrpc > 10.5.17.21.1491:  udp 28 (DF)
15:03:15.683641 10.5.17.21 > 10.21.109.46: icmp: 10.5.17.21 udp port 1491
unreachable [tos 0xc0]

-----------------------
On my pc:
windump -p udp
15:03:10.320679 IP platone.replynet.prv.1491 > ttsat.111: udp 56
15:03:25.319739 IP platone.replynet.prv.1491 > ttsat.111: udp 56
15:03:55.332502 IP platone.replynet.prv.1491 > ttsat.111: udp 56

Can someone help me?
Thanks

Massimo