You can configure Extreme Switch using the following steps:
enable sflow
configure sflow agent {LOOPBACK_INTERFACE_NAME}
configure sflow collector {NETFLOW_SERVER_IP} port {NETFLOW_SERVER_LISTENER_PORT}
configure sflow sample-rate 512
configure sflow poll-interval 60
enable sflow backoff-threshold
configure sflow backoff-threshold 500
enable sflow ports all