Overview

The SNMP Interface Event Monitor watches for changes in the status for each port on your switches, routers, and other devices that support SNMP. It can also monitor the error rate on each interface and alert if it exceeds the thresholds that you choose.

Use Cases

• Monitoring network interfaces for errors and discards
• Monitoring rates for different kinds of network packets
• Detecting changes in interface operational status

Monitoring Options

This event monitor provides the following options:

SNMP Version

Select the SNMP version that will be used to collect the inventory data. The best version to use will depend on how your network devices have been configured. Most devices support SNMPv1, but some may require SNMPv2 or SNMPv3.

Community

Enter the SNMP community string that will be used to connect. The community string is equivalent to a password. The default community string for read-only access is "public" so use this value if you are unsure of what community string your devices are configured to use. The community string is only required for SNMPv1 and SNMPv2c connections. SNMPv3 uses different authentication parameters.

Port Number

The standard port number for SNMP requests is 161. If your devices have been configured to use a different port, you can specify it here.

Timeout

The timeout tells the event monitor how long to wait for a response. The default value is best for almost all situations, but you can increase or decrease it if you choose.

Retries

Since SNMP runs on UDP, packet delivery and response are not guaranteed. For this reason it is good practice to tell the event monitor to retry one or more times if it does not receive a response.

Username (SNMPv3 Only)

Specify the user name that will be used when connecting to the network device. This is a required value for the SNMPv3 protocol.

Context (SNMPv3 Only)

In rare cases a context string is required to establish the SNMPv3 connection. If required by your devices, enter it here. This value is optional.

Security Level (SNMPv3 Only)

SNMPv3 connections can support both authentication and privacy. Authentication means that a valid passphrase must be supplied, or the SNMP unit will not accept the connection. Privacy means that the connection to the SNMP device must be encrypted, otherwise the device will not accept it. Both are optional. If your devices do not require either, select noAuthNoPriv. If you devices require authentication but not privacy, select authNoPriv. If your devices require both authentication and privacy, select authPriv.

Auth. Protocol Level (SNMPv3 Only)

If authNoPriv or authPriv is selected for the security level, you must specify the authentication protocol for the connection. Supported values are MD5, SHA, SHA-224, SHA-256, SHA-384 and SHA-512. Consult the documentation and configuration of your network devices to determine which protocol they support.

Auth. Passphrase (SNMPv3 Only)

Enter the authentication passphrase that your SNMP devices have been configured to accept. This value is required when authNoPriv or authPriv is selected for the security level.

Privacy Protocol (SNMPv3 Only)

If authPriv is selected for the security level, the privacy protocol must be selected. The supported values are DES and AES.

Priv. Passphrase (SNMPv3 Only)

Enter the privacy passphrase that your SNMP devices have been configured to accept. This value is required when authPriv is selected for the security level.

Alert with [Info/Warning/Error/Critical] if the device cannot be contacted by SNMP

Use this option to select how you will be alerted if the network device cannot be contacted or does not respond to SNMP requests.

Alert with [Info/Warning/Error/Critical] if an interface status changes

Use this option to select how you will be alerted if the status of any interface changes. For example, if it changes from up to down, an alert will be generated.

Alert if the error rate on any interface exceeds a specified value

To calculate the error rate, the event monitor adds the values for ifInErrors and ifOutErrors and calculates the error rate based on the sum and the time since the last check.

Include the list of interface statuses in each notification

With this option selected, the event monitor will include a list of all interfaces and the status that was detected for each.

Filters

Use the filters option to select which interfaces will be checked. You can choose to monitor all interfaces, only specific interfaces or all interfaces except for a list that you specify. To specify the interfaces to include or ignore, enter their numeric indexes in a list separated by commas. For example, ".1, .2, .9".

Authentication and Security

For SNMPv1 and SNMPv2c, a community string for the device being monitored is required. For SNMPv3, a username and other SNMPv3 parameters are required.

Protocols

Data Points

This event monitor generates the following data points:

Data Point	Description
Errors	The total error rate.
Status	The detected status at the time the event monitor last ran.
Incoming Discards	The number of incoming packet discards.
Incoming Errors	The number of incoming errors.
Incoming NUCast	The rate of incoming non-unicast packets.
Incoming UCast	The rate of incoming unicast packets.
Outgoing Discards	The number of outgoing discards.
Outgoing Errors	The number of outgoing errors.
Outgoing NUCast	The rate of outgoing non-unicast packets.
Outgoing Queue Length	The length of the outgoing queue.
Outgoing UCast	The rate of outgoing unicast packets.

Sample Output

Tutorial

To view the tutorial for this event monitor, click here.