Sflow - Dell S4810 Reference Manual

sFlow

The Dell Networking operating software (OS) supports sFlow commands on the S4810 platform.
Dell Networking operating software 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.
• Dell Networking operating software 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 sFlow sampling functionality is supported only for egress traffic and not for ingress traffic.
• 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
extended-switch
1542
enable).
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