Concept Guide

• If the interface states are up and the sampling rate is not congured on the port, the default sampling rate is calculated based on the
line speed.
• If the interface states are shut down, the sampling rate is set using the global sampling rate.
• If the global sampling rate is non-default, for example 256, and if the sampling rate is not congured on the interface, the sampling rate
of the interface is the global non-default sampling rate, that is, 256.
To avoid the back-o, either increase the global sampling rate or congure all the line card ports with the desired sampling rate even if
some ports have no sFlow congured.
Important Points to Remember
• The Dell EMC Networking OS implementation of the sFlow MIB supports sFlow conguration 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 Conguration 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
backo mechanism is automatically applied to reduce this amount. Some sampled packets may be dropped when the exported packet
rate is high and the backo mechanism is about to or is starting to take eect. The dropEvent counter, in the sFlow packet, is always
zero.
• Community list and local preference elds are not lled in extended gateway element in the sFlow datagram.
• 802.1P source priority eld is not lled in extended switch element in sFlow datagram.
• Only Destination and Destination Peer AS number are packed in the dst-as-path eld 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) eld in the extended switch element is not packed in case of routed packet.
• The destination VLAN eld 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 specic 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 congure 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.
828
sFlow