Administrator Guide

● If the global sampling rate is non-default, for example 256, and if the sampling rate is not configured on the interface, the
sampling rate of the interface is the global non-default sampling rate, that is, 256.
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.
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
fields 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.
● Confirm that extended information packing is enabled.
show sflow
The bold line shows that extended sflow setting is enabled for extended switch.
DellEMC#show sflow
sFlow services are enabled
Egress Management Interface sFlow services are disabled
Global default sampling rate: 32768
Global default counter polling interval: 20
Global default extended maximum header size: 128 bytes
Global extended information enabled: switch
1 collectors configured
Collector IP addr: 100.1.1.1, Agent IP addr: 1.1.1.2, UDP port: 6343 VRF: Default
0 UDP packets exported
3 UDP packets dropped
0 sFlow samples collected
stack-unit 1 Port set 0
Hu 1/2/1: configured rate 131072, actual rate 131072
DellEMC#
sFlow
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