Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.100.0 - Page 782

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 Extended sFlow Extended sFlow packs additional information in the sFlow datagram depend on the type of sampled packet. The platform supports extended-switch information processing only. Extended sFlow packs additional information in the sFlow datagram depending on the type of sampled packet. You can enable the following options: • extended-switch - 802.1Q VLAN ID and 802.1p priority information. • extended-router - Next-hop and source and destination mask length. • extended-gateway - Source and destination AS number and the BGP next-hop. NOTE: The entire AS path is not included. BGP community-list and local preference information are not included. These fields are assigned default values and are not interpreted by the collector. • Enable extended sFlow. sflow [extended-switch] [extended-router] [extended-gateway] enable By default packing of any of the extended information in the datagram is disabled. • Confirm that extended information packing is enabled. show sflow Examples of Verifying Extended sFlow The bold line shows that extended sFlow settings are enabled on all three types. Dell#show sflow sFlow services are enabled Egress Management Interface sFlow services are disabled 782 sFlow