HP Cisco Catalyst Blade Switch 3020 Cisco Catalyst Blade Switch 3020 for HP So - Page 477

SNMP Notifications, SNMP ifIndex MIB Object Values, Interface Type, ifIndex Range

Page 477 highlights

Chapter 25 Configuring SNMP Understanding 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. SNMP ifIndex MIB Object Values In an NMS, the IF-MIB generates and assigns an interface index (ifIndex) object value that is a unique number greater than zero to identify a physical or a logical interface. When the switch reboots or the switch software is upgraded, the switch uses this same value for the interface. For example, if the switch assigns a port 2 an ifIndex value of 10003, this value is the same after the switch reboots. The switch uses one of the values in Table 25-3 to assign an ifIndex value to an interface: Table 25-3 ifIndex Values Interface Type SVI1 EtherChannel Loopback Tunnel Physical (such as Gigabit Ethernet or SFP2-module interfaces) Null 1. SVI = switch virtual interface 2. SFP = small form-factor pluggable ifIndex Range 1-4999 5000-5012 5013-5077 5078-5142 10000-14500 14501 Note The switch might not use sequential values within a range. OL-8915-01 Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide 25-5

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25-5
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
OL-8915-01
Chapter 25
Configuring SNMP
Understanding 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.
SNMP ifIndex MIB Object Values
In an NMS, the IF-MIB generates and assigns an interface index (ifIndex) object value that is a unique
number greater than zero to identify a physical or a logical interface. When the switch reboots or the
switch software is upgraded, the switch uses this same value for the interface. For example, if the switch
assigns a port 2 an ifIndex value of 10003, this value is the same after the switch reboots.
The switch uses one of the values in
Table 25-3
to assign an ifIndex value to an interface:
Note
The switch might not use sequential values within a range.
Table 25-3
ifIndex Values
Interface Type
ifIndex Range
SVI
1
1.
SVI = switch virtual interface
1–4999
EtherChannel
5000–5012
Loopback
5013–5077
Tunnel
5078–5142
Physical (such as Gigabit Ethernet or SFP
2
-module interfaces)
2.
SFP = small form-factor pluggable
10000–14500
Null
14501