Concept Guide

sFlow

sFlow is a standard-based sampling technology embedded within switches and routers which is used to monitor network trac. It is

designed to provide trac monitoring for high-speed networks with many switches and routers.

Topics:

• Overview

• Implementation Information

• Enabling Extended sFlow

• Enabling and Disabling sFlow on an Interface

• Enabling sFlow Max-Header Size Extended

• sFlow Show Commands

• Conguring Specify Collectors

• Changing the Polling Intervals

• Back-O Mechanism

• sFlow on LAG ports

• Enabling Extended sFlow

Overview

The Dell EMC Networking Operating System (OS) supports sFlow version 5.

sFlow is a standard-based sampling technology embedded within switches and routers which is used to monitor network trac. It is

designed to provide trac monitoring for high-speed networks with many switches and routers. sFlow uses two types of sampling:

• Statistical packet-based sampling of switched or routed packet ows.

• Time-based sampling of interface counters.

The sFlow monitoring system consists of an sFlow agent (embedded in the switch/router) and an sFlow collector. The sFlow agent resides

anywhere within the path of the packet and combines the ow samples and interface counters into sFlow datagrams and forwards them to

the sFlow collector at regular intervals. The datagrams consist of information on, but not limited to, packet header, ingress and egress

interfaces, sampling parameters, and interface counters.

Application-specic integrated circuits (ASICs) typically complete packet sampling. sFlow collector analyses the sFlow datagrams received

from dierent devices and produces a network-wide view of trac ows.

Implementation Information

Dell EMC Networking sFlow is designed so that the hardware sampling rate is per line card port-pipe and is decided based on all the ports

in that port-pipe.

If you do not enable sFlow on any port specically, the global sampling rate is downloaded to that port and is to calculate the port-pipe’s

lowest sampling rate. This design supports the possibility that sFlow might be congured on that port in the future. Back-o is triggered

based on the port-pipe’s hardware sampling rate.

For example, if port 1 in the port-pipe has sFlow congured with a 16384 sampling rate while port 2 in the port-pipe has sFlow congured

but no sampling rate set, the system applies a global sampling rate of 512 to port 2. The hardware sampling rate on the port-pipe is then set

at 512 because that is the lowest congured rate on the port-pipe. When a high trac situation occurs, a back-o is triggered and the

928 sFlow