trisul_udpsink : A UDP sink to prevent ICMP unreachable
Trisul uses high speed packet filter mechainsms in Netflow mode as well. This means that Trisul does not actually open a UDP port 2055 (netflow) to process netflow but directly taps into the packet filter mechanisms.
The downside of this is since there is no port open but the packets are directed at those ports, you may see
ICMP Dest Unreachable messages.
The trisul_udpsink program simply opens these ports and reads the messages into a sink. This stops the ICMP messages.
Running the service
The preferred method is to edit the trisul-udpsink systemd service.
If you are using the default NETFLOW port 2055
systemctl start trisul-udpsink
If you want to change the port number from 2055 to your custom port. Type.
systemctl edit trisul-udpsink --full
Change the port number from 2055 to your preferred.
If you need more than one port number , just clone the systemd file to create new services with different port numbers.
Running the program directly
You can run the program manually like so
There are other options for sending it into the background as a daemon. Type