Users Guide

Implementation Information
Dell Networking sFlow is designed so that the hardware sampling rate is per line card port-pipe and is decided based on all the ports
in that port-pipe.
If you do not enable sFlow on any port specically, the global sampling rate is downloaded to that port and is to calculate the port-
pipe’s lowest sampling rate. This design supports the possibility that sFlow might be congured on that port in the future. Back-o is
triggered based on the port-pipe’s hardware sampling rate.
For example, if port 1 in the port-pipe has sFlow congured with a 16384 sampling rate while port 2 in the port-pipe has sFlow
congured but no sampling rate set, Dell Networking OS applies a global sampling rate of 512 to port 2. The hardware sampling rate
on the port-pipe is then set at 512 because that is the lowest congured rate on the port-pipe. When a high trac situation occurs, a
back-o is triggered and the hardware sampling rate is backed-o from 512 to 1024. Note that port 1 maintains its sampling rate of
16384; port 1 is unaected because it maintains its congured sampling rate of 16484.
To avoid the back-o, either increase the global sampling rate or congure all the line card ports with the desired sampling rate even
if some ports have no sFlow congured.
Important Points to Remember
• The Dell Networking OS implementation of the sFlow MIB supports sFlow conguration 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
Conguration and EIS modes respectively.
• sFlow sampling is done on a per-port basis.
• Dell Networking OS exports all sFlow packets to the collector. A small sampling rate can equate to many exported packets. A
backo mechanism is automatically applied to reduce this amount. Some sampled packets may be dropped when the exported
packet rate is high and the backo mechanism is about to or is starting to take eect. The dropEvent counter, in the sFlow
packet, is always zero.
• Community list and local preference elds are not lled in extended gateway element in the sFlow datagram.
• 802.1P source priority eld is not lled in extended switch element in sFlow datagram.
• Only Destination and Destination Peer AS number are packed in the dst-as-path eld 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) eld in the extended switch element is not packed in case of routed packet.
• The destination VLAN eld in the extended switch element is not packed in a Multicast packet.
• Up to 700 packets are sampled and processed per second.
Enabling and Disabling sFlow
By default, sFlow is disabled globally on the system.
Use the following command to enable sFlow globally.
• Enable sFlow globally.
CONFIGURATION mode
[no] sflow enable
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 specic interface, use the following command.
796
sFlow