13.3. Configuring agents in sFlowTrend-Pro
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13.3. Configuring agents in sFlowTrend-Pro

An sFlow agent is responsible for sending sFlow data to sFlowTrend-Pro from a switch (or router) or a host. In the case of a switch or router, one agent will be associated with the device, and the IP address of the agent will normally be the same (or one of the) IP address used for the switch. Switches can be configured to send sFlow from sFlowTrend-Pro using SNMP, or alternatively the switch can be manually configured. For hosts, normally the agent runs on a physical host. This agent can send data for both that host, and any virtual machines that are running on that host. Hosts are configured to send sFlow either through DNS or manually.

Select the → Configure agents menu item to launch the Configure agents dialog. This dialog contains a table which lists all the agents that sFlowTrend-Pro is receiving sFlow from. For switches, it also allows you to change the SNMP settings for each switch, and to tell sFlowTrend-Pro about switches that it should configure via SNMP to send sFlow.

The table includes the following columns:

Status

This column uses color coded symbols to indicate the overall status of the agent:

The agent is enabled and sFlowTrend-Pro is receiving sFlow (and, if the agent is a switch or router, it can communicate with the switch using SNMP).

The agent is disabled, but sFlowTrend-Pro is receiving sFlow from it. Or, if the agent is a switch, then either sFlowTrend-Pro is receiving CLI configured sFlow from it, and sFlowTrend-Pro is unable to communicate with the switch via SNMP to get the interface names, or sFlowTrend-Pro is still in the process of configuring sFlow on the switch. See Section 14.1.7, “sFlowTrend-Pro cannot communicate with the switch using SNMP”.

The agent is enabled, but sFlowTrend-Pro is not receiving sFlow. If the agent is a switch, then this can also mean sFlowTrend-Pro cannot communicate with the switch using SNMP to enable it. See Section 14.1.6, “sFlowTrend-Pro is not receiving sFlow from a switch or host” and Section 14.1.7, “sFlowTrend-Pro cannot communicate with the switch using SNMP”.

The agent is disabled and sFlowTrend-Pro is not receiving sFlow from it.

A switch setting has been changed in the Configure agents dialog, but the change has not been deployed (operation pending). sFlowTrend-Pro will deploy the change when you click the OK button.

The tooltip for the status symbol gives more detail on the status of the agent.

Type

The type column displays the type of agent: whether it is a switch or a host:

The agent is a switch or router.

The agent is a host.

The agent is both a switch/router and a host.

DNS name
The domain name obtained from the reverse DNS lookup of the SNMP IP address of the agent.
SNMP IP address
The IP address that sFlowTrend-Pro will use to communicate with the agent, if it is a switch, via SNMP to obtain the friendly system and interface names. This is also the IP address that sFlowTrend-Pro will use when using SNMP to configure the switch to send sFlow, if Configure via SNMP is selected.
sFlow agent address
The IP address that is used by the sFlow agent to uniquely identify itself. This address is learnt from the sFlow data and cannot be changed in sFlowTrend-Pro. For a switch, in many cases the sFlow agent address will be the same as the SNMP IP address. However if the switch is switching between multiple VLANs, the sFlow agent address may be in a VLAN that is not routable to the host that is running sFlowTrend-Pro. In which case you can change the SNMP IP address to tell sFlowTrend-Pro how to communicate with the switch.
Enable
Check this checkbox if you would like sFlowTrend-Pro to receive and store data for this agent. You can use the checkbox in the title row for the header to enable or disable all agents.
Configure sFlow via SNMP
For a switch, check this checkbox if you would like sFlowTrend-Pro to use SNMP to configure the switch to send sFlow.
Use global SNMP settings
For a switch, check this box if you would like sFlowTrend-Pro to use the global SNMP settings (see Section 13.2.3, “Configuring global SNMP settings”) when communicating with the switch using SNMP. If this box is not checked you can specify the SNMP settings for this switch by clicking on the button. sFlowTrend-Pro uses SNMP to query the switch for the systemGroup and ifTable, so that it can present friendly names for the switch and its interfaces. If sFlowTrend-Pro is to use SNMP to configure the switch to send sFlow, these settings must allow write access to the sFlow MIB.
Edit
Although most of the commonly changed agent settings can be edited in the table, for a switch you can edit all the settings and view the detailed status of the switch by clicking on this button.
Delete
Delete the agent from the sFlowTrend-Pro and stop further data collection. If this agent has been configured by SNMP to send sFlow, sFlowTrend-Pro will disable sFlow before deleting the switch.

You can click with the left button on a column heading to sort the table by that column. You can also click with the Shift+left mouse button to add secondary sort columns.

Any changes made to agents and their settings will not be implemented until the OK button is clicked.

13.3.1. Adding a switch configured via SNMP

Clicking on the Add switch agent button launches a dialog that allows you to enter the details for a new switch. This should be used when you wish to tell sFlowTrend-Pro about a switch that should be configured via SNMP to send sFlow. Enter the following information:

SNMP IP address
The IP address that sFlowTrend-Pro should use when communicating with the switch via SNMP.
Use global SNMP settings
Check this box if you would like sFlowTrend-Pro to use the global SNMP settings (see Section 13.2.3, “Configuring global SNMP settings”). If this box is unchecked, you can click on Change SNMP settings to specify the SNMP settings specific to this switch. You can ask sFlowTrend-Pro to communicate with the switch using SNMP v2c or v3. Make sure that the SNMP settings that you enter will allow sFlowTrend-Pro write access to the sFlow MIB.
Enable
Check this box if you want sFlowTrend-Pro to enable and start collecting data from this switch. sFlowTrend allows data to be collected from only five switches, so if five switches are already enabled, the Enable checkbox will be inactive and you must disable one of the other switches before you can enable the new switch.
Configure sFlow via SNMP
Check this box if sFlowTrend-Pro is to use SNMP to configure the switch to send sFlow.

sFlowTrend-Pro will not configure the switch until the Configure agents dialog has been closed by clicking the OK button.

13.3.2. Verifying switch configuration and status

Once you have submitted the changes that you have made in the Configure agents dialog, by clicking the OK button, when you go to the Network, Interfaces, Counters, Top N, Circles, or Root cause tabs and select a switch, the sFlowTrend-Pro status bar (see Section 1.1, “Introducing sFlowTrend-Pro”) will show the status of the switch that is currently selected. The message in the status bar will give information on whether sFlowTrend-Pro can communicate with the selected switch using SNMP, has successfully used SNMP to configure the selected switch to send sFlow (if this option has been chosen), and whether sFlowTrend-Pro is receiving sFlow from the selected switch.

You can also view the status of a switch by selecting the → Configure agents menu item to launch the Configure agents dialog and then viewing the tooltip for the color coded switch status symbol or using the edit button to view the detailed status of a switch (see above).

The status message will also indicate if there is a problem with the configuration, for example:

No SNMP
sFlowTrend-Pro cannot communicate with the switch using SNMP. Verify that the sFlowTrend-Pro is using the correct SNMP settings and that there are no firewalls in the network or on the host that are blocking SNMP. See Section 14.1.7, “sFlowTrend-Pro cannot communicate with the switch using SNMP” for troubleshooting tips.
Cannot configure sFlow with SNMP - SNMP write access denied
sFlowTrend-Pro is not using the correct SNMP settings that allow write access to the sFlow MIB or the switch is not configured to allow SNMP set from the system running sFlowTrend-Pro.
Cannot configure sFlow with SNMP - no sFlow MIB
The switch cannot be configured via SNMP to send sFlow. Instead, you must use the switch CLI to configure sFlow (see Appendix A, Configuring switches to send sFlow.
Already in use
Another application has already configured this switch to send sFlow and there are no additional resources to send sFlow to sFlowTrend-Pro as well. Disable the other application so that the switch can be configured by sFlowTrend-Pro. You can identify the other applications which have already configured the switch by using the edit button. The Additional switch details section, under Other owners lists the IP addresses of the other systems which have configured the switch, together with a description of the application. Alternatively, you can configure sFlowTrend-Pro so that it removes the other application's claim on the switch and replaces it with its own (see Section 15.1, “Server custom configuration settings”, sflowtrend.useForce).

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