Cisco Catalyst 2950 Command Reference Manual page 464

snmp-server host
Usage Guidelines SNMP notifications can be sent as traps or inform requests. Traps are unreliable because the receiver
does not send acknowledgments when it receives traps. The sender cannot determine if the traps were
received. However, an SNMP entity that receives an inform request acknowledges the message with an
SNMP response PDU. If the sender never receives the response, the inform request can be sent again.
Thus, informs are more likely to reach their intended destinations.
However, informs consume more resources in the agent and in the network. Unlike a trap, which is
discarded as soon as it is sent, an inform request must be held in memory until a response is received or
the request times out. Traps are also sent only once, but an inform might be retried several times. The
retries increase traffic and contribute to a higher overhead on the network.
If you do not enter an snmp-server host command, no notifications are sent. To configure the switch to
send SNMP notifications, you must enter at least one snmp-server host command. If you enter the
command with no keywords, all trap types are enabled for the host. To enable multiple hosts, you must
enter a separate snmp-server host command for each host. You can specify multiple notification types
in the command for each host.
When multiple snmp-server host commands are given for the same host and kind of notification (trap
or inform), each succeeding command overwrites the previous command. Only the last snmp-server
host command is in effect. For example, if you enter an snmp-server host inform command for a host
and then enter another snmp-server host inform command for the same host, the second command
replaces the first.
The snmp-server host command is used with the snmp-server enable traps global configuration
command. Use the snmp-server enable traps command to specify which SNMP notifications are sent
globally. For a host to receive most notifications, at least one snmp-server enable traps command and
the snmp-server host command for that host must be enabled. Some notification types cannot be
controlled with the snmp-server enable traps command. For example, some notification types are
always enabled. Other notification types are enabled by a different command.
The no snmp-server host command with no keywords disables traps, but not informs, to the host. To
disable informs, use the no snmp-server host informs command.
Examples This example shows how to configure a unique SNMP community string named comaccess for traps and
prevent SNMP polling access with this string through access list 10:
Switch(config)# snmp-server community comaccess ro 10
Switch(config)# snmp-server host 172.20.2.160 comaccess
Switch(config)# access-list 10 deny any
This example shows how to send the SNMP traps to the host specified by the name myhost.cisco.com.
The community string is defined as comaccess.
Switch(config)# snmp-server enable traps
Switch(config)# snmp-server host myhost.cisco comaccess snmp
This example shows how to enable the switch to send all traps to the host myhost.cisco using the
community string public:
Switch(config)# snmp-server enable traps
Switch(config)# snmp-server host myhost.cisco public
This example shows how to enable the switch to send EnvMon traps to the host myhost.cisco using the
community string public:
Switch(config)# snmp-server host myhost.cisco version 2c public envmon
Catalyst 2950 and Catalyst 2955 Switch Command Reference
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Chapter 2 Catalyst 2950 and 2955 Cisco IOS Commands
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