Chapter 1 sFlow
Configuration
When configuring sFlow, go to these
sections for information you are interested in:
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sFlow
Overview
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Configuring
sFlow
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Displaying
sFlow
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sFlow
Configuration Example
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Troubleshooting
sFlow Configuration
Based on packet
sampling, Sampled Flow (sFlow) is a traffic monitoring technology mainly used to
collect and analyze traffic statistics.
sFlow has the following two sampling
mechanisms:
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Packet-based sampling: Samples one packet out of
a specified number of packets from an sFlow enabled port.
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Time-based sampling: Samples interface
statistics at a specified interval from an sFlow enabled port.
The sFlow system involves an sFlow agent embedded
in a device and a remote sFlow collector. The sFlow agent collects traffic from
the sFlow enabled ports, encapsulates the information into sFlow packets, and sends
the packets to the sFlow collector. The sFlow collector analyzes the sFlow
packets and displays the results.
As a traffic monitoring technology, sFlow
has the following advantages:
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Supports traffic monitoring on Gigabit and
higher-speed networks.
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Provides scalability with one sFlow collector
monitoring multiple or more sFlow agents.
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Implements the low-cost sFlow agent.
Currently, only the
sFlow agent function is supported on S5500-EI Series Ethernet Switches.
1.1.2 Operation of sFlow
sFlow operates
as follows:
1)
With sFlow enabled, a physical port encapsulates
received data into packets and sends them to the sFlow agent.
2)
The sFlow agent periodically collects interface
statistics on all sFlow enabled ports.
3)
When the sFlow packet buffer overflows or the
one-second timer expires, the sFlow agent sends the sFlow packets to the
specified sFlow collector.
Follow these steps to configure sFlow:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Configure an IP address for the sFlow
agent
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sflow agent ip ip-address
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Required
Not configured by default.
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Specify the IP address and port number of
the sFlow collector
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sflow collector ip ip-address [ port port-num ]
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Required
Not specified by default.
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Set the sFlow interval
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sflow interval interval-time
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Optional
20 seconds by default.
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Enter interface view
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interface interface-type interface-number
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—
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Enable sFlow in the inbound or outbound direction
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sflow enable
{ both | inbound | outbound }
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Required
Not enabled by default.
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Specify the sFlow sampling mode
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sflow sampling-mode { determine | random }
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Optional
random by
default.
Currently, the determine mode is
not supported on S5500-EI series Ethernet switches.
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Specify the sFlow sampling rate
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sflow sampling-rate rate
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Optional
200000 by default.
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Caution:
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The sFlow agent and sFlow collector must not
have the same IP address.
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Currently, you can specify at most two sFlow
collectors on S5500-EI Series Ethernet Switches.
1.3 Displaying
sFlow
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To do…
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Use the command…
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Remarks
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Display sFlow configuration information
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display sflow
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Available in any view
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I. Network requirements
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Host A and Server are connected to Switch
through GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 respectively.
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Host B works as an sFlow collector with IP
address 3.3.3.2 and port number 6343, and is connected to Switch through
GigabitEthernet 1/0/3.
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GigabitEthernet 1/0/3 belongs to VLAN 1, having
an IP address of 3.3.3.1.
Run sFlow agent on Switch, and enable sFlow
on GigabitEthernet 1/0/1 to monitor traffic on this interface. Switch sends
sFlow packets through GigabitEthernet 1/0/3 to Host B, which then analyzes the
sFlow packets and displays the results.
II. Network diagram
Figure
1-1 Network diagram for sFlow configuration
III. Configuration procedure
# Configure
an IP address for the sFlow agent.
<Switch>
system-view
[Switch]
sflow agent ip 3.3.3.1
# Specify
the IP address and port number of the sFlow collector.
[Switch]
sflow collector ip 3.3.3.2
# Set the sFlow interval to 30 seconds.
[Switch] sflow interval 30
# Enable sFlow in both the inbound and outbound
directions on GigabitEthernet 1/0/1.
[Switch] interface GigabitEthernet 1/0/1
[Switch-GigabitEthernet1/0/1] sflow
enable both
# Specify the traffic sampling rate.
[Switch-GigabitEthernet1/0/1] sflow
sampling-rate 100000
# Display the sFlow configuration
information.
[Switch-GigabitEthernet1/0/1] display
sflow
sFlow Global Information:
Agent IP:3.3.3.1
Collector
IP:3.3.3.2 Port: 6343
Interval(s): 30
sFlow Port
Information:
Interface
Direction Rate Mode Status
GE1/0/1
Both 100000 Random Active
I. Symptom
The remote sFlow collector cannot receive
sFlow packets.
II. Analysis
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sFlow is not enabled globally because the sFlow
agent or/and the sFlow collector are not specified.
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No port is enabled with sFlow to sample data.
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The IP address of the sFlow collector specified
on the sFlow agent is different from that of the remote sFlow collector.
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No IP address is configured for the Layer 3
interface on the device, or the IP address is configured, but the UDP packets
with the IP address being the source cannot reach the sFlow collector.
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The physical link between the device and the
sFlow collector fails.
III. Solution
1)
Check whether sFlow is correctly configured by
displaying sFlow configuration with the display sflow command.
2)
Check whether the correct IP address is
configured for the device to communicate with the sFlow collector.
3)
Check whether the physical link between the
device and the sFlow collector is normal.
