Concept Guide
Back-O Mechanism
If the sampling rate for an interface is set to a very low value, the CPU can get overloaded with ow samples under high-trac conditions.
In such a scenario, a binary back-o mechanism gets triggered, which doubles the sampling-rate (halves the number of samples per
second) for all interfaces. The backo mechanism continues to double the sampling-rate until the CPU condition is cleared. This is as per
sFlow version 5 draft. After the back-o changes the sample-rate, you must manually change the sampling rate to the desired value.
As a result of back-o, the actual sampling-rate of an interface may dier from its congured sampling rate. You can view the actual
sampling-rate of the interface and the congured sample-rate by using the show sflow command.
sFlow on LAG ports
When a physical port becomes a member of a LAG, it inherits the sFlow conguration from the LAG port.
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 elds
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.
• Conrm 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.
DellEMC#show sflow
sFlow services are enabled
Egress Management Interface sFlow services are disabled
Global default sampling rate: 32768
Global default counter polling interval: 20
Global default extended maximum header size: 128 bytes
Global extended information enabled: none
1 collectors configured
Collector IP addr: 100.1.1.1, Agent IP addr: 1.1.1.2, UDP port: 6343 VRF: Default
0 UDP packets exported
0 UDP packets dropped
0 sFlow samples collected
stack-unit 1 Port set 0
Gi 1/1: configured rate 16384, actual rate 16384
DellEMC#
If you did not enable any extended information, the show output displays the following (shown in bold).
DellEMC#show sflow
sFlow services are disabled
832
sFlow