Concept Guide

To avoid the back-off, either increase the global sampling rate or configure all the line card ports with the desired sampling rate
even if some ports have no sFlow configured.
Important Points to Remember
● The Dell EMC Networking OS implementation of the sFlow MIB supports sFlow configuration via snmpset.
● By default, sFlow collection is supported only on data ports. If you want to enable sFlow collection through management
ports, use the management egress-interface-selection and application sflow-collector commands in
Configuration and EIS modes respectively.
● Dell EMC Networking OS exports all sFlow packets to the collector. A small sampling rate can equate to many exported
packets. A backoff mechanism is automatically applied to reduce this amount. Some sampled packets may be dropped when
the exported packet rate is high and the backoff mechanism is about to or is starting to take effect. The dropEvent counter,
in the sFlow packet, is always zero.
● Community list and local preference fields are not filled in extended gateway element in the sFlow datagram.
● 802.1P source priority field is not filled in extended switch element in sFlow datagram.
● Only Destination and Destination Peer AS number are packed in the dst-as-path field in extended gateway element.
● If the packet being sampled is redirected using policy-based routing (PBR), the sFlow datagram may contain incorrect
extended gateway/router information.
● The source virtual local area network (VLAN) field in the extended switch element is not packed in case of routed packet.
● The destination VLAN field in the extended switch element is not packed in a Multicast packet.
● Up to 700 packets can be sampled and processed per second.
Enabling and Disabling sFlow on an Interface
By default, sFlow is disabled on all interfaces.
This CLI is supported on physical ports and link aggregation group (LAG) ports.
To enable sFlow on a specific interface, use the following command.
● Enable sFlow on an interface.
INTERFACE mode
[no] sflow ingress-enable
To disable sFlow on an interface, use the no version of this command.
Enabling sFlow Max-Header Size Extended
To configure the maximum header size of a packet to 256 bytes, use the following commands:
● Set the maximum header size of a packet.
CONFIGURATION mode
INTERFACE mode
sflow max-header-size extended
By default, the maximum header size of a packet is 128 bytes. When sflow max-header-size extended is enabled,
256 bytes are copied. These bytes are useful for VxLAN, NvGRE, IPv4, and IPv6 tunneled packets.
NOTE: Interface mode configuration takes priority.
● To reset the maximum header size of a packet, use the following command
[no] sflow max-header-size extended
● View the maximum header size of a packet.
show running-config sflow
Example of the show sflow command when the sflow max-header-size extended is configured globally
DellEMC(conf-if-gi-1/10)#show sflow
sFlow services are enabled
Egress Management Interface sFlow services are disabled
sFlow
781