Cisco IOS NetFlow is a flexible and extensible method to record network performance data. It efficiently provides a key set of services for IP applications, including network traffic accounting, usage-based network billing, network planning, security, Denial of Service monitoring capabilities, and network monitoring. NetFlow provides valuable information about network users and applications, peak usage times, and traffic routing.

By polling the Netflow MIB of a Netflow-enabled Cisco router at configured intervals, this test collects a wide variety of per-flow statistics on traffic on that Cisco router. With the help of these metrics, you can quickly identify the net flow on which a large amount of data was transacted, who the talkers were, the type of communication that they engaged in, and also instantly drill down to the interfaces impacted by this communication.

When users complaint of a network slowdown, knowing which two hosts are engaged in a bandwidth-intensive communication is sure to take you closer to determining what activity the two hosts were performing, and whether it can be terminated to conserve bandwidth.

Note:

This test will work only if Netflow is enabled on a router. To achieve this, follow the steps below:

• Enter global configuration mode on the router or MSFC, and issue the following commands for each interface on which you want to enable NetFlow:

  interface {interface} {interface_number}
  ip route-cache flow
  bandwidth <kbps>
  exit

  This enables NetFlow on the specified interface alone. Remember that on a Cisco IOS device, NetFlow is enabled on a per-interface basis. The bandwidth command is optional, and is used to set the speed of the interface in kilobits per second.

• Then, issue the following command to break up long-lived flows into 1-minute fragments. You can choose any number of minutes between 1 and 60. If you leave it at the default of 30 minutes your traffic reports will have spikes. It is important to set this value to 1 minute in order to generate alerts and view troubleshooting data.

  ip flow-cache timeout active 1

• Next, issue the following command to ensure that flows that have finished are periodically exported. The default value is 15 seconds. You can choose any number of seconds between 10 and 600.

  ip flow-cache timeout inactive 15

• Finally, enable ifIndex persistence (interface names) globally. This ensures that the ifIndex values are persisted during device reboots.

  snmp-server ifindex persist

This page depicts the default parameters that need to be configured for the NetFlowTest.

• The TEST PERIOD list box helps the user to decide how often this test needs to be executed. 

• Specify the port number through which the device exposes its SNMP MIB in the SNMPPORT text box. The default value is 161.

• By default, the eG agent supports SNMP version 1. Accordingly, the default selection in the SNMPVERSION list is v1. However, if a different SNMP framework is in use in your environment, say SNMP v2 or v3, then select the corresponding option from this list.

• Specify the SNMP community name that the test uses to communicate with the device in the SNMPCOMMUNITY text box. This parameter is specific to SNMP v1 and v2 only. Therefore, if the SNMPVERSION chosen is v3, then this parameter will not appear.

• The USERNAME parameter appears only when v3 is selected as the SNMPVERSION. SNMP version 3 (SNMPv3) is an extensible SNMP Framework which supplements the SNMPv2 Framework, by additionally supporting message security, access control, and remote SNMP configuration capabilities. To extract performance statistics from the MIB using the highly secure SNMP v3 protocol, the eG agent has to be configured with the required access privileges ? in other words, the eG agent should connect to the MIB using the credentials of a user with access permissions to be MIB. Therefore, specify the name of such a user against the USERNAME parameter.

• The CONTEXT parameter appears only when v3 is selected as the SNMPVERSION. An SNMP context is a collection of management information accessible by an SNMP entity. An item of management information may exist in more than one context and an SNMP entity potentially has access to many contexts. A context is identified by the SNMPEngineID value of the entity hosting the management information (also called a contextEngineID) and a context name that identifies the specific context (also called a contextName). If the USERNAME provided is associated with a context name, then the eG agent will be able to poll the MIB and collect metrics only if it is configured with the context name as well. In such cases therefore, specify the context name of the USERNAME in the CONTEXT text box. By default, this parameter is set to none.

• Specify the password that corresponds to the above-mentioned USERNAME in the AUTHPASS text box. This parameter once again appears only if the SNMPVERSION selected is v3.

• Confirm the AUTHPASS by retyping it in the CONFIRM PASSWORD text box.

• The AUTHTYPE parameter too appears only if v3 is selected as the SNMPVERSION. From the AUTHTYPE list box, choose the authentication algorithm using which SNMP v3 converts the specified USERNAME and PASSWORD into a 32-bit format to ensure security of SNMP transactions. You can choose between the following options:

  • MD5 ? Message Digest Algorithm
  • SHA ? Secure Hash Algorithm

• The ENCRYPTFLAG flag appears only when v3 is selected as the SNMPVERSION. By default, the eG agent does not encrypt SNMP requests. Accordingly, the ENCRYPTFLAG is set to NO by default. To ensure that SNMP requests sent by the eG agent are encrypted, select the YES option.

• If the ENCRYPTFLAG is set to YES, then you will have to mention the encryption type by selecting an option from the ENCRYPTTYPE list. SNMP v3 supports the following encryption types:

  • DES ? Data Encryption Standard
  • AES ? Advanced Encryption Standard

• Specify the encryption password in the ENCRYPTPASSWORD text box.

• Confirm the encryption password by retyping it in the CONFIRM PASSWORD text box.

• Specify the maximum duration (in seconds) for which the test will wait for a response from the router in the TIMEOUT text box.

• This test captures statistics on traffic to destinations, where each destination host is by default represented by its IP address in the eG monitoring console. Accordingly, the REPORT HOST NAMES flag is set to No by default. You can set this flag to Yes so that the names of the individual hosts are displayed in the eG monitoring console instead of their IP addresses.

• By default, the value 3 is displayed in the MINIMUM FLOW PERCENT text box. This indicates that, by default, the test will consider only those destinations that are using 3% or more of current traffic. You can increase or decrease this value based on your monitoring needs. If you set this value to 0, then all net flows will be monitored.

• By default, the REPORT NO OF FLOWS LIMIT parameter is set to all indicating that this test will monitor all destinations by default. If you want the test to report, say only the top 5 destinations in terms of the amount of traffic they generate in their net flows, then set this value to 5.

• By default, the IGNORE LOCAL TRAFFIC flag is set to Yes, indicating that the test will ignore the destinations of all the intranet traffic on the router. If you want the test to report metrics pertaining to the destinations of local traffic as well, set this flag to No.

• By default, in an IT environment, all data transmission occurs over UDP. Some environments however, may be specifically configured to offload a fraction of the data traffic - for instance, certain types of data traffic or traffic pertaining to specific components - to other protocols like TCP, so as to prevent UDP overloads. In such environments, you can instruct the eG agent to conduct the SNMP data traffic related to the monitored target over TCP (and not UDP). For this, set the DATA OVER TCP flag to Yes. By default, this flag is set to No.

• Once the necessary values have been entered, clicking on the Update button will register the changes made.

When changing default configurations of tests, the values with "$" indicate variables that will be replaced by the eG system according to the specific server being managed - for instance, $hostName is the host/nickname of the target host, $port is the port number of the server being monitored. E.g., for a server xyz:80, $hostName will be changed automatically by the eG manager to "xyz" and $port will be changed to "80" when configuring a test.