Reference Guide

sFlow | 1083
39
sFlow
Overview
sFlow commands are supported on the Dell Force10 platforms. The symbols e c s z under
command headings indicate which Dell Force10 platforms — E-Series, C-Series, S-Series or Z-Series,
respectively — support the command.
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 Force10 recommends that the sFlow Collector be connected to the Dell Force10 chassis
through a line card port rather than the RPM Management Ethernet port.
• FTOS exports all sFlow packets to the sFlow Collector. A small sampling rate can equate to a large
number of exported packets. A backoff mechanism will automatically be 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, will always be 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 PBR (Policy-Based Routing), 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 VLAN field in the extended switch element will not be packed in case of a routed
packet.
• The destination VLAN field in the extended switch element will not be packed in case of 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 (see sflow
extended-switch enable)
— 1600 packets when extended-router and/or extended-gateway information packing is enabled
(see Figure and sflow extended-gateway enable)