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27-5
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 27 Configuring SNMP
Configuring SNMP
SNMP Notifications
SNMP allows the switch to send notifications to SNMP managers when particular events occur. SNMP
notifications can be sent as traps or inform requests. In command syntax, unless there is an option in the
command to select either traps or informs, the keyword traps refers to either traps or informs, or both.
Use the snmp-server host command to specify whether to send SNMP notifications as traps or informs.
Note SNMPv1 does not support informs.
Traps are unreliable because the receiver does not send an acknowledgment when it receives a trap, and
the sender cannot determine if the trap was received. When an SNMP manager receives an inform
request, it acknowledges the message with an SNMP response protocol data unit (PDU). If the sender
does not receive a response, the inform request can be sent again. Because they can be re-sent, informs
are more likely than traps to reach their intended destination.
The characteristics that make informs more reliable than traps also consume more resources in the switch
and in the network. Unlike a trap, which is discarded as soon as it is sent, an inform request is held in
memory until a response is received or the request times out. Traps are sent only once, but an inform
might be re-sent or retried several times. The retries increase traffic and contribute to a higher overhead
on the network. Therefore, traps and informs require a trade-off between reliability and resources. If it
is important that the SNMP manager receive every notification, use inform requests. If traffic on the
network or memory in the switch is a concern and notification is not required, use traps.
Configuring SNMP
This section describes how to configure SNMP on your switch. It contains this configuration
information:
• Default SNMP Configuration, page 27-5
• SNMP Configuration Guidelines, page 27-6
• Disabling the SNMP Agent, page 27-7
• Configuring Community Strings, page 27-7
• Configuring SNMP Groups and Users, page 27-9
• Configuring SNMP Notifications, page 27-11
• Setting the Agent Contact and Location Information, page 27-14
• Limiting TFTP Servers Used Through SNMP, page 27-15
• SNMP Examples, page 27-15
Default SNMP Configuration
Table 27-3 shows the default SNMP configuration.