How does device availability monitoring work in OpManager and how do I choose the appropriate protocol for my network?

OpManager uses monitoring protocols to continuously monitor the uptime and availability of your network devices. You can choose between the three primary availability monitoring protocols - ICMP, TCP and SNMP based on your business needs and the size of for your network. OpManager displays the availability (uptime), packet loss and response time of any device in your network at any given time. Given below is a brief explanation on which monitoring protocol to choose based on the nature of your network.

Monitoring via ICMP

This protocol is suited best for environments that are ICMP (ping) enabled. ICMP is the default protocol that is chosen by OpManager during device discovery. OpManager sends ping packets to the destination (monitored) device and the device availability, packet loss and response time is calculated based on the ping response pattern received from the monitored device. This ping response pattern varies for different operating systems.

OpManager recommends ICMP protocols for large networks and ICMP (ping) enabled environments. The polling mechanism is comparatively faster than other protocols and this helps you discover devices in your networks that bring in considerable amount of load. ICMP is the default configuration with which the devices are discovered irrespective of the nature of your environment. If your environment doesn't support ICMP, you can change the availability monitoring protocol as TCP or SNMP for devices in bulk post discovery. Unlike other protocols, ICMP does not require any additional configurations (selective ports to be opened in your firewall) to be carried out. The default ping packet size is 1 for Windows and 2 Linux operating systems.

Native Ping: In case the ICMP protocol is restricted in a network, OpManager enables "native ping" for an uninterrupted availability monitoring. Upon every restart, if OpManager identifies that the ICMP is enabled, the native ping is automatically disabled and availability monitoring is continued using ICMP. Alternatively, users can also configure OpManager to use TCP and SNMP for availability monitoring if ICMP is disabled in their environment.

Monitoring via TCP

Here, the availability of the configured device is calculated based on the successful socket connection between the OpManager server and the TCP port of the monitored device.

TCP based availability monitoring is most suitable for ping disabled environments or networks that solely prefer TCP port based monitoring for security reasons. OpManager recommends using this protocol for TCP enabled environments that does not attract abundant traffic, i.e., medium scaled networks. OpManager discovers devices using ICMP by default, but can be changed later from the Inventory or individual snapshot pages.

Additional configurations required:

TCP configured port should be allowed by the antivirus or your firewall. The specified port can be any available port between the industry specified range of 0 and 65,535.

How do I enable TCP monitoring?

• Go to the respective device snapshot page, click on the Edit device details option and select TCP option under 'Availability Monitoring Via'.
• To perform this action in bulk, select the devices from the Inventory and choose 'Monitor Availability via TCP' from the Inventory Actions.

Monitoring via SNMP

SNMP based availability monitoring can only be configured and used if all the device are SNMP implemented. This requires SNMP credentials to be associated with all the monitored devices.

OpManager supports SNMP v1,v2 and v3 credentials. An SNMP ping request is sent to the destination device and the availability monitoring is calculated based on the successful SNMP response from the device. If the SNMP credentials expire, the associated device will be notified as unreachable and marked as Down. The data loss in SNMP based availability monitoring is close to zero and is recommended for medium scaled networks.

Additional configurations required:

• SNMP ports should be specified and enabled while configuring the credentials.
• The SNMP port (default port 161) configured should not be allowed in the antivirus or firewall.
• Make sure the SNMP credentials are not periodically expired for continuous availability monitoring.
• Make sure there are no lag in the SNMP response from the devices in your network. If encountered, the SNMP timeout can be increased according to your network. (Note: An increased timeout value may result in an overall delay in availability monitoring.)

How do I enable SNMP monitoring?

• Go to the respective device snapshot page and click on the Edit device details option.
• Select SNMP option under 'Availability Monitoring Via' and select the appropriate credential (SNMP v1/v2/v3).
• To perform this action in bulk, select the devices from the Inventory and choose 'Associate credentials' option from the Inventory Actions. Select the appropriate SNMP v1/v2/v3 credential and click on Save.

Please check the below pages to know more about availability monitoring in OpManager:
Availability monitoring in OpManager
Device availability states and severity
Scalability and hardware recommendations