JUNOS High Availability

SNMP Configuration

SNMP is a topic covered by most books about networking, so we do not discuss it here in detail. However, we can’t write a chapter on network monitoring without at least mentioning it. In a nutshell, SNMP helps you monitor the state of devices in the network.

The protocol supports both on-event and on-demand generation of chassis state information. Event-triggered notices are called SNMP traps. Traps are triggered when certain conditions, such as link failure, authentication failure, or chassis restarts, occur on a managed chassis. The trap notifications are sent to one or more defined host workstations or servers that have been configured to receive the traps. Chassis state information can be obtained on demand by using variations of Get commands issued from host workstations or servers back to the managed chassis.

JUNOS SNMP Configuration

In this configuration sample, SNMP is enabled on router r1. Some SNMP-driven management tools are able to populate a GUI based on content within the Get responses and the trap notifications. For this reason, the administrator chooses to define a system name, r1-J2350, and the location where the chassis is physically sitting, Frederick_ MD (arguably the friendliest city in the United States).

The administrator also defines two community strings, public and private, to control SNMP access to the chassis. A community string acts as a keyword of sorts, in that the host systems must use it to run Get commands on the managed device. Community ...