a value from an agent or store a value into the agent. The agent gathers data from the MIB, the repository for information about device parameters and network data. The agent can also respond to a manager's requests to get or set data. An agent can send unsolicited traps to the manager. Traps are messages alerting the SNMP manager to a condition on the network. Traps can mean improper user authentication, restarts, link status (up or down), MAC address tracking, closing of a TCP connection, loss of connection to a neighbor, or other significant events.
This example shows how to permit any SNMP manager to access all objects with read-only permission using the community string public. The switch also sends VTP traps to the hosts 192.180.1.111 and 192.180.1.33 using SNMPv1 and to the host 192.180.1.27 using SNMPv2C. The community string public is sent with the traps:
Switch(config)# snmp-server community public Switch(config)# snmp-server enable traps vtp Switch(config)# snmp-server host 192.180.1.27 version 2c public Switch(config)# snmp-server host 192.180.1.111 version 1 public Switch(config)# snmp-server host 192.180.1.33 public
SPAN / RSPAN
You can analyze network traffic passing through ports or VLANs by using SPAN to send a copy of the traffic to another port on the switch that has been connected to a SwitchProbe device or other Remote Monitoring (RMON) probe. SPAN mirrors received or sent (or both) traffic on a source port and received traffic on one or more source ports or source VLANs, to a destination port for analysis.
Only traffic that enters or leaves source ports or traffic that enters source VLANs can be monitored by using SPAN; traffic that gets routed to ingress source ports or source VLANs cannot be monitored. For example, if incoming traffic is being monitored, traffic that gets routed from another VLAN to the source VLAN is not monitored; however, traffic that is received on the source VLAN and routed to another VLAN is monitored.
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