Users Guide

hardware sampling rate is backed-off from 512 to 1024. Note that port 1 maintains its sampling rate of 16384; port 1 is unaffected because
it maintains its configured sampling rate of 16384.:
• If the interface states are up and the sampling rate is not configured on the port, the default sampling rate is calculated based on the
line speed.
• If the interface states are shut down, the sampling rate is set using the global sampling rate.
• 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 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 and Disabling sFlow on an Interface
By default, sFlow is disabled on all interfaces.
This CLI is supported on physical ports and link aggregation group (LAG) ports.
To enable sFlow on a specific interface, use the following command.
• Enable sFlow on an interface.
INTERFACE mode
[no] sflow ingress-enable
To disable sFlow on an interface, use the no version of this command.
Enabling sFlow Max-Header Size Extended
To configure the maximum header size of a packet to 256 bytes, use the following commands:
• Set the maximum header size of a packet.
CONFIGURATION mode
INTERFACE mode
sflow max-header-size extended
sFlow
765