Enterasys Networks Security Router X-PeditionTM - Manual (Page 75)

Network Management through SNMP
XSR User’s Guide 2-39
SNMP Informs
SNMP Informs were first introduced in SNMPv2. An Inform is essentially nothing more than an
acknowledged trap. That is, when a remote application receives an Inform it sends back an “I got
it” message. When you send an Inform you use the remote engineID with the message and the
securityName and engineID exist as a pair in the Remote User table. The SNMP trap program
discovers the remote engineID as other applications would and creates the SNMPv3 message with
the proper user that the remote side is expecting to receive.
SNMP v3 on the XSR is supported by several CLI and SNMP agent enhancements. SNMP v1/v2c
traps can be configured with remote IP addresses to send traps with the
snmp-server host
command. For SNMP v3, each agent has a unique identifier - the engine ID - which is used to
configure users in the User Security Model (USM). With the SNMP v3 USM, the XSR requires
configuration of remote engine IDs and remote users.
To set up an inform recipient, first set the engine ID of the remote SNMP entity with snmp-server
engineID . USM users may then be added with snmp-server user . Complete the configuration
using snmp-server host to specify remote SNMP entities that will receive informs. The snmp-
server informs command can be used to change the global retry, timeout and queue default
settings. The snmp-server enable traps command remains the same in all SNMP versions. This
command enables both traps and informs.
For a full description of SNMP commands, refer to the XSR CLI Reference Guide. Also refer to
NetSight Atlas Router Services Manager v2.0 documentation to query and change SNMP values.
Because the SNMP manager is disabled at boot-up, you must either manually enable the SNMP
manager using the CLI, or enable it in
startup-config .
Shaping Trap Traffic
Two controls are available to manage network traffic caused by SNMP traps. The first, set by the
snmp-server min-trap-spacing command, configures minimum spacing between successive
traps to ensure that they are spaced without causing delay and cap the number of packets
generated by traps.
The second control defines the maximum number of traps that can be sent in a given time
window. The time window is a moving sum of the number of traps sent to the network. If the
number of traps sent in the previous window-time is less than the value set by the
snmp-server
max-traps-per-window command, then more traps can be sent.
Both methods work simultaneously and independently and only when both are satisfied will a
trap be sent. Otherwise, traps will be queued and sent as soon as conditions satisfy both traffic
shaping methods.
Statistics
The XSR supports SNMP gets for MIBs listed in “Chapter 1: Network Management “of the XSR
CLI Reference Guide. Also, refer to NetSight Atlas Router Services Manager v2.0 to query and
change SNMP values.