Macro 32 Ramblings

Juniper supports flow exports by sampling packet headers with the routing engine and aggregating them into flows. Packet sampling is acheived by defining a firewall filter to accept and sample all traffic, applying that rule to an interface, and then configuring the sampling forwarding option.

interfaces {
    ge-0/1/0 {
        unit 0 {
            family inet {
                filter {
                    input all;
                    output all;
                }
                address /  (< - This is in binary notation)
            }
        }
    }
}
		
firewall {
    filter all {
        term all {
            then {
                sample;
                accept;
            }
        }
    }
}
		
forwarding-options {
    sampling {
        input {
            family inet {
                rate 100;
            }
        }
        output {
            cflowd  {
                port ;
                version ;
            }
        }
    }
}