Dell S4820T, Configuration Manual

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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 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 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 Extended sFlow
The S-Series platforms support
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
Examples of Verifying Extended sFlow
The bold line shows that extended sFlow settings are enabled on all three types.
Dell#show sflow
sFlow services are enabled
Egress Management Interface sFlow services are disabled
sFlow
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