Concept Guide

hardware sampling rate is backed-o from 512 to 1024. Note that port 1 maintains its sampling rate of 16384; port 1 is unaected because it
maintains its congured sampling rate of 16384.:
• 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 Extended sFlow
Extended sFlow packs additional information in the sFlow datagram depend on the type of sampled packet. The platform supports
extended-switch information processing only.
Extended sFlow packs additional information in the sFlow datagram depending on the type of sampled packet. You can enable the following
options:
• extended-switch — 802.1Q VLAN ID and 802.1p priority information.
• extended-router — Next-hop and source and destination mask length.
• extended-gateway — Source and destination AS number and the BGP next-hop.
NOTE
: The entire AS path is not included. BGP community-list and local preference information are not included. These elds
are assigned default values and are not interpreted by the collector.
• Enable extended sFlow.
sflow [extended-switch] [extended-router] [extended-gateway] enable
By default packing of any of the extended information in the datagram is disabled.
• Conrm that extended information packing is enabled.
show sflow
sFlow
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