The Dell Networking Operating System (OS) supports sFlow version 5.
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 sFlow is not enabled on any port, the global sampling rate is downloaded to that port and is used to calculate the port-pipe’s lowest sampling rate. This design supports the possibility that sFlow might be configured on that port in the future. Back-off is triggered based on the port-pipe’s hardware sampling rate.
The default global sampling rate is 32768. The sampling rates are determined as follows:
The Dell Networking OS implementation of the sFlow MIB supports sFlow configuration using snmpset.
By default, sFlow collection is supported only on data ports. 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 sent in the extended gateway element in the sFlow datagram.
802.1P source priority field is not sent in the extended switch element in the 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 the case of a 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.
| Command | Parameters |
FTOS# configuration |
Enter configuration mode. |
FTOS(conf)# sflow enable |
Enable sFlow globally. |
FTOS(conf)# sflow collector <IP ADDR> agent-addr <IP ADDR> |
Set the collector IP address (external device managing sFlow data). Set the agent IP address (this or another switching devices that gather data). |
FTOS(conf)# sflow max-header-size extended |
(Optional) By default, the maximum header size of a packet is 128 bytes. When sFlow max-header-size extended is enabled, 256 bytes are copied. These bytes are useful for VxLAN, NvGRE, IPv4, and IPv6 tunneled packets. |
FTOS(conf)#sflow extended-switch enable |
Extended sFlow packs additional information in the sFlow datagram depending on the type of sampled packet. 802.1Q VLAN ID and 802.1P priority information. |
FTOS(conf)#sflow polling-interval <15-86400> |
(Optional) Set a specific polling interval to be compatible with the collector. |
FTOS(conf)#sflow sample-rate <256-8388608> |
(Optional) Set a specific sample rate to be compatible with the collector. (Only powers of 2. for example, 4096 8192). |
| Command | Parameters |
FTOS# Configuration |
Enter configuration mode. |
FTOS(conf)# interface te 0/10 |
Enter the specific interface. |
FTOS(conf-if-te-0/10)# sflow ingress-enable |
Enable sFlow on the interface. |
FTOS(conf-if-te-0/10)#sflow max-header-size extended |
(Optional) By default, the maximum header size of a packet is 128 bytes. When sFlow max-header-size extended is enabled, 256 bytes are copied. These bytes are useful for VxLAN, NvGRE, IPv4, and IPv6 tunneled packets. |
FTOS(conf-if-te-0/10)#sflow polling-interval <15-86400> |
(Optional) Set a specific polling interval to be compatible with the collector. |
FTOS(conf-if-te-0/10)#sflow sample-rate <256-8388608> |
(Optional) Set a specific sample rate to be compatible with the collector. (Only powers of 2, for example 4096 8192) |
FTOS# show sflow sFlow services are enabled Global default sampling rate: 32768 Global default counter polling interval: 20 1 collectors configured Collector IP addr: 133.33.33.53, Agent IP addr: 133.33.33.116, UDP port: 6343 77 UDP packets exported 0 UDP packets dropped 165 sFlow samples collected 69 sFlow samples dropped due to sub-sampling
FTOS# show sflow interface tengigabitethernet 1/1 Te 1/1 sFlow type :Ingress Configured sampling rate :16384 Actual sampling rate :16384 Counter polling interval :20 Extended max header size :128 Samples rcvd from h/w :0
FTOS# show running-config interface tengigabitethernet 1/16 !interface TenGigabitEthernet 1/16 no ip address switchport sflow ingress-enable sflow sample-rate 8192 no shutdown