[Solved] Iptables and logging

Hello Forum,

I have two networks and a OpenWRT router between them. The private network on the eth1 switch ports ( and the public net on the wan port eth0 ( I want to log udp packets coming from the public network, because there are some windows machines. They send udp broadcasts on port 137/138.
iptables -I INPUT -p udp -i eth0 -j LOG --log-level info --log-prefix "Windows UP "

What I dont understand is why this rule also logs my windows machines in the private net. For example this packet:
Windows UP IN=eth0 OUT= MAC=ff:ff:ff:ff:ff:ff:12:34:56:78:90:12:08:00 SRC= DST= LEN=78 TOS=0x00 PREC=0x00 TTL=128 ID=20514 PROTO=UDP SPT=137 DPT=137 LEN=58

On the eth0 interface is the network and not the 0 net. Broadcasts like should not be forwarded into the net

root@LEDE:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface         UG    0      0        0 eth0   U     0      0        0 eth0 UH    0      0        0 eth0   U     0      0        0 eth1

What could I reconfigured in the OpenWRT router?

Thanks a lot