Hi,
I am running Linux Kernel 2.4.20 and iptables 1.2.7a, with a Linux server
doing primarly SNAT work for masquerading. I don't seem to be able to
forward UDP packets with iptables. I am able to forward TCP packets through
the firewall, such as identd requests, like so:
iptables -t nat -A PREROUTING -j DNAT -p tcp --destination-port 113
--to-destination xxx.xxx.xxx.xxx
What I'm doing here is forwarding a packet from an external system to a
machine on an internal network, so that it can answer an identd request.
The above works fine for that. However, it doesn't seem to work for UDP
packets. Even when I forward all data from the source IP address to an
internal host (as opposed to limiting it by --destination-port), the UDP
data refuses to be forwarded, and my linux machine sends out ICMP port
unreachable errors to the external machine. No data is sent across the
local ethernet at all.
Is there any reason for this? Anything I'm doing wrong or can change to
correct it? Any help would be greatly appreciated.
