Simple Network Management Protocol (SNMP) is an Internet standard protocol for managing all devices on an IP network. SNMP has centralized systems called clients (which SNMP calls managers) that actively monitor servers (which SNMP calls agents) by querying them and collecting status information and statistics from them. The managers generally run on dedicated computers called Network Management Systems (NMSs), and routers are one type of agent.
When you want the NMS on your network to be able to monitor the device, you need to configure the device to be an SNMP agent (Chapter 6 looks at some of this configuration):
 user@junos-device# set snmp community public authorization read-only
To transform the router into an agent, you place the router into an SNMP community using set snmp community public authorization read-only. This command uses one of the common SNMP communities, public. The second part of the command defines how the agent (your Junos OS) will respond to requests from the NMS system. An authorization of read-only means that the device will send its information to the NMS, but the NMS will not be able to modify any settings on the device (which it could do if you specified an authorization of read-write). You can configure the device to respond to multiple communities, each with its own authorization level.
You can configure basic information about the device for the NMS to collect when it queries the ...