I have seen continually this message in IPFilter log file.
Jul 2 20:30:33 nas3a ipmon: [ID 702911 local0.warning] 20:30:32.565073 2x e1000g4 @0:11 b 10.20.30.40,138 -> 10.20.30.255,138 PR udp len 20 250 IN low-ttl
The port 138 belongs netbios according to /etc/services file:
# cat /etc/services | grep 138
netbios-dgm 138/tcp # NETBIOS Datagram Service
netbios-dgm 138/udp # NETBIOS Datagram Service
So I wondering what the message is trying to do. Is it a broadcast one? Blocking it will have any impact?