Creating SNMP Health Checks

An SNMP health monitor sends an SNMPv1, SNMPv2c, or SNMPv3 request to the monitored server. The SNMP agent in the managed server provides the data in the form of variables, and each variable is associated with an unique OID (object identifier). An OID is a dotted-decimal number that defines the location of the object in the universal MIB tree. You can manually enter up to 15 OIDs to be monitored by the SNMP monitor. The server is considered available if the response received from the server matches the expected result for all OIDs. If the server does not respond after a specified number of requests, the server is declared down by the monitor.

Complete the following steps to create an SNMP Health Check monitor:

Go to Configure > Networking > DNS > DTC > DTC Health Checks.
Click Create DTC Health Check > SNMP.
Configure the following in the SNMP Health Monitor dialog:
- Name: Enter a name for the SNMP health monitor.
- Description: Enter a description for the health monitor.
- Port: Specify a port number.
- Interval (seconds): Enter the interval value in seconds. The health monitor runs only for the specified interval and it is measured from the begining of the previous monitor cycle. The default value is 15.
- Timeout (seconds): Enter the timeout value in seconds. The monitor waits for the number of seconds that you specify after sending a request. If the monitor does not receive a response within the number of seconds that you specify, then it considers this check as failed. The monitor discards any response it receives after the timeout. The default value is 10.
- Retries for Healthy Status: Enter an integer value. This value determines how many valid responses or good health checks in a row must be received by the monitor from the DTC server.
- Retries for Down Status: Enter an integer value. It is the opposite of the Retries for Healthy Status count. This value determines how many unhealthy status health checks (server is unavailable) in a row must be collected by the monitor from the DTC server.
- Version: Select the SNMP version, v1, v2c, or v3. Note that the available options for versions v1 and v2c differ from those for v3 version.
- (SNMPv1 and SNMPv2c only) Community: Enter the text string that the SNMP monitor must send along with the queries to the server for authentication. The community string is similar to a password and the server accepts queries only from the SNMP monitor that provide the correct community string. Note that this community string must match exactly what you enter in the management system. The default value is public.
  - SNMP OID Entries: Configure the following if you have selected the SNMP Version as v1 or v2. Click Add and configure the following:
  - OID: Specify the object identifier. An OID is a unique dotted-decimal number that identifies the location of the object in the MIB tree. For more information about OIDs, see SNMP MIB Hierarchy.
  - Type: Select either String or Integer from the drop-down list.
  - Operator: Select one of these operators from the drop-down list: Any, Equals, Larger or equals, Range, and Smaller or equals.
  - Value: If the operator is Equals, Larger or equals, or Smaller or equals, enter a value. If the operator is Range, enter the minimum and maximum values in the Min value and Max value fields respectively.
  - Comment: Enter information about the SNMP OID entry.
- SNMP v3 Settings: Configure the following if you have selected v3:
  - Context Engine ID: Enter the context engine ID of the SNMP agent in the form of 10 to 64 hexadecimal digits (5 to 32 octet numbers). This can be empty unless multiple SNMP agents with different context engine IDs are running on the remote host.
  - Context Name: Specify the name of the collection that contains the requested OIDs. Should be empty unless the SNMP agent has multiple such collections.
  - Existing SNMP Credentials: If you select this option, choose the credential from the drop-down.
  - New SNMP Credentials: If you select this option, configure the following and click Save:
    - Authentication Protocol: Select one of the following:
      - MD5: Select this to use the HMAC-MD5-96 authentication protocol to authenticate the SNMPv3 user.
        This protocol uses the MD5 (Message-Digest algorithm 5) hash function in HMAC (Hash-based Message Authentication Code) and truncates the output to 96 bits. The output is included as part of the SNMP message sent to the receiver. For detailed information about the protocol, refer to RFC1321, The MD5 Message-Digest Algorithm.
      - SHA: Select this to use the HMAC-SHA-96 authentication protocol to authenticate the SNMPv3 user.
        This protocol uses the SHA (Secure Hash Algorithm) hash function and truncates the output to 96 bits. The output is included as part of the SNMP message sent to the receiver.
      - None: Select this to decline using any authentication protocol for this SNMPv3 user. When you select this option, you are not required to enter a password.
        Password: Enter a password for the selected authentication protocol.
        Confirm Password: Enter the same password.
    - Privacy Protocol: Select one of the following:
      - DES: Select this to use DES for data encryption. DES is a block cipher that employs a 56-bit key size and 64-bit block size in the encryption.
      - AES: Select this to use AES for data encryption. AES is a symmetric-key encryption standard that comprises AES-128 block cipher. The cipher has a 128-bit block size and a key size of 128 bits.
      - None: Select this to decline using any privacy protocol for this SNMPv3 user. When you select this option, you are not required to enter a password.
        Password: Enter a password for the privacy protocol.
        Confirm Password: Enter the same password.
Click Save & Close.