Specifications

Using sFlow
ExtremeWare XOS 11.0 Concepts Guide 143
Using sFlow
sFlow® is a technology for monitoring traffic in data networks containing switches and routers. It relies
on statistical sampling of packets from high-speed networks, plus periodic gathering of the statistics. A
User Datagram Protocol (UDP) datagram format is defined to send the information to an external entity
for analysis. sFlow consists of a Management Information Base (MIB) and a specification of the packet
format for forwarding information to a remote agent. Details of sFlow specifications can be found in
RFC 3176, and specifications and more information can be found at the following website:
http://www.sflow.org
The ExtremeWare XOS implementation is based on sFlow version 5, which is an improvement from the
revision specified in RFC 3176. Additionally, the switch hardware allows you to set the hardware
sampling rate independently for each module on the switch, instead of requiring one global value for
the entire switch. The switch software also allows you to set the individual port sampling rates, so you
can fine-tune the sFlow statistics gathering.
However, you should be aware of a few limitations in the current release (11.0). The current release
supports:
• Generic port statistics reported to the sFlow collector
• Non-extended data
• Only those packets that do not match an ACL rule are considered for sampling
• Only port-based sampling
• No MIB support
Configuring sFlow
ExtremeWare XOS allows you to collect sFlow statistics in hardware on a per port basis. An agent,
residing locally on the switch, sends data to a collector that resides on another machine. You configure
the local agent, the address of the remote collector, and the ports of interest for sFlow statistics
gathering. You can also modify default values for how frequently on average a sample is taken and the
maximum number of samples allowed before throttling the sample gathering.
To configure sFlow on a switch, you must do the following tasks:
• Configure the local agent
• Configure the addresses of the remote collectors
• Enable sFlow globally on the switch
• Enable sFlow on the desired ports
Optionally, you may also change the default values of the following items:
• How often the statistics are collected
• How frequently a sample is taken, globally or per port
• How many samples per second can be sent to the CPU