28-5
Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
78-11380-10
Chapter28 Configuring SNMP Configuring SNMP
Figure28-1 SNMP Network
For information on supported MIBs and how to access them, see Appendix A, “Supported MIBs.”

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 the re 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.
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 discar ded as s oon a s i t i s sen t, a n info rm r equ es t i s h eld i n
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.
Note SNMPv1 does not support informs.
Configuring SNMP
This section describes how to configure SNMP on your switch. It contains this c onfigurati on
information:
•Default SNMP Configuration, page 28-6
•SNMP Configuration Guidelines, page 28-6
•Disabling the SNMP Agent, page 28-7
•Configuring Community Strings, page 28-7
•Configuring SNMP Groups and Users, page 28-9
•Configuring SNMP Notifications, page 28-11
•Setting the Agent Contact and Location Information, page 28-14
•Limiting TFTP Servers Used Through SNMP, page 28-14
•SNMP Examples, page 28-15
Get-request, Get-next-request,
Get-bulk, Set-request Network device
Get-response, traps
43581
SNMP Manager
NMS
MIB
SNMP Agent