I am butting my head here folks for the past few days and hopefully someone will be able to help me. Background: We receive streaming udp traffic from two sources destined for port 8302. They are always sending this traffic whether are box is on or not. Just keeps on coming. We want to split off the traffic from one of the sources and redirect it to port 9302. They will not do this for us, so we need to use a REDIRECT rule in the nat table to do this. With every other chain empty and with an ACCEPT policy: iptables -t nat -A PREROUTING -p udp -s <source2 ip> --dport 8302 -j REDIRECT --to-ports 9302 however, traffic from source2 keeps on hitting 8302. Doing a iptables -t nat -L -n -v shows: 0 0 REDIRECT udp -- * * <source2 ip> 0.0.0.0/0 udp dpt:8302 redir ports 9302 So the traffic is never getting picked up by the chain. Even doing a general rule in the nat PREROUTING with no target shows that no traffic is hitting: 0 0 udp -- * * <source2 ip> 0.0.0.0/0 This is a very simple box with only 1 interface (eth0). I thought this may be due to connection tracking so I added a raw entry to NOTRACK the traffic also: Chain PREROUTING (policy ACCEPT 90101 packets, 12M bytes) 9491 1333K NOTRACK all -- * * <source2 ip> 0.0.0.0/0 So I see the raw chain is picking it up.. But it is skipping past the nat chain. Does anyone know why this is occurring? One other thing to note is this traffic is being natted first by a cisco router. But tcpdump shows it coming in as follows: 11:53:27.133025 IP <source2 ip>.32811 > 192.168.6.165.8302: UDP, length 255 11:53:27.133585 IP <source2 ip>.32811 > 192.168.6.165.8302: UDP, length 74 11:53:27.133876 IP <source2 ip>.32811 > 192.168.6.165.8302: UDP, length 74 11:53:27.335457 IP <source2 ip>.32811 > 192.168.6.165.8302: UDP, length 74 etc Any help or ideas would be greatly appreciated. -- Jeremy Freeman etc etc
