Via the web interface:
Navigate to: System->sFlow
Select "Receiver Configuration"
Receiver Owner: 1
Receiver IP : IP of server
Tick "No timeout"
Select "Sampler configuration"
Set Sampler Datasource (anything)
Receiver Index as "Receiver Owner" above, e.g. 1
Sampler rate: 1024
On a Linux server, receiving the SFlow packets. Get sflowtool-3.25, untag it/build.
Create a tcpdump format capture of incoming data:
./sflowtool -t > a.cap
View it in tcpdump:
tcpdump -r a.cap