Hi, Look at this topology. 192.168.1.1 10.0.0.1 10.0.0.2 172.0.0.1 ------------ ------------------- -------------- ------------ | PC 1 |----------------| NAT (linux) |---------------------------| router |----------------------| PC 2 | ------------ ------------------- -------------- ------------ 192.168.1.100 172.0.0.100 Configure "iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE" on NAT(linux) with two different version kernel. On PC1, ping 172.0.0.100 -t 3, PC2 can be reached with both kernel version. ping 172.0.0.100 -t 2, I got 2 different results with 2 different kernel version on NAT(linux). I got ttl-expired icmp response from router with old version, but got no response at all with upgrade kernel version. No matter with which kernel version, router sends ttl-expired icmp response from 10.0.0.2 to 10.0.0.1. It's forwarded to the internal network by old version kernel, but considered as the traffic to the local process by the upgraded version kernel. Notice that ping 172.0.0.100 -t 3 works well in both cases. It seems like the old version performed as a Cone NAT, well the upgraded one performed as a symmetric NAT. So, what's the default NAT type if I set rule as "iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE", full cone NAT, port restricted cone NAT, restricted cone NAT, or symmetric NAT? Can this be configurable? If it's configurable, how to do that? Thanks. Sean. -- To unsubscribe from this list: send the line "unsubscribe netfilter" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html