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Reference Guide

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sFlow
The Dell Networking operating software (FTOS) supports sFlow commands on the Z-Series platform.
FTOS sFlow monitoring system includes an sFlow Agent and an sFlow Collector.
• The sFlow Agent combines the flow samples and interface counters into sFlow datagrams and forwards them to
the sFlow Collector.
• The sFlow Collector analyses the sFlow Datagrams received from the different devices and produces a network-
wide view of traffic flows.
Important Points to Remember
• Dell Networking recommends that the sFlow Collector be connected to the Dell Networking chassis through a
line card port rather than the route processor module (RPM) Management Ethernet port.
• FTOS exports all sFlow packets to the sFlow 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.
• sFlow sampling is done on a per-port basis.
• Community list and local preference fields are not filled up in the extended gateway element in the sFlow
datagram.
• The 802.1P source priority field is not filled up in the extended switch element in the sFlow datagram.
• Only Destination and Destination Peer AS numbers are packed in the dst-as-path field in the 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.
• sFlow does not support packing extended information for IPv6 packets. Only the first 128 bytes of the IPv6 packet
is shipped in the datagram.
• The source virtual local area network (VLAN) field in the extended switch element is not packed if there is a
routed packet.
• The destination VLAN field in the extended switch element is not packed if there is a multicast packet.
• The maximum number of packets that can be sampled and processed per second is:
– 7500 packets when no extended information packing is enabled.
– 7500 packets when only extended-switch information packing is enabled (refer to sflow extended-
switch enable).
– 1600 packets when extended-router and/or extended-gateway information packing is enabled (refer to
sflow extended-gateway enable)
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