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Chapter 8 User Authentication
40 Avaya P334T-ML User’s Guide
control the P330.
Manager/Agent Communication
There are several ways that the SNMP manager and the agent communicate.
The manager can:
• Retrieve a value – a get action
The SNMP manager requests information from the agent, such as the link status
of an Ethernet port or the number of good packets received on the switch. The
agent gets the value of the requested MIB variable and sends the value back to
the manager.
• Retrieve the value immediately after the variable you name – a get-next action.
The SNMP manager retrieves values from the MIB tree. Using the get-next
function, you do not need to know the exact variable name you are looking for.
The SNMP manager takes the variable you name and then uses a sequential
search to find the desired variable.
• Retrieve a number of values – a get-bulk action
The get-bulk operation retrieves the specified number of instances of the
requested MIB variable. This minimizes the number of protocol exchanges
required to retrieve a large amount of data.
L Get-bulk is not supported in SNMPv1.
• Change a setting on the agent – a set action
The SNMP manager requests the agent to change the value of the MIB variable.
For example, you can enable or disable a port.
• An agent can send an unsolicited message to the manager at any time if a
significant, predetermined event takes place on the agent. This message is called
a trap.
When a trap condition occurs, the SNMP agent sends an SNMP trap message to
the specified trap receiver or trap host. The SNMP Administrator configures the
trap host, usually the SNMP management station, to perform the action needed
when a trap is detected.
SNMPv1
SNMPv1 uses community strings to limit access rights. Each SNMP device is
assigned to a read community and a write community. To communicate with a
switch, you must send an SNMP packet with the relevant community name.
By default, if you communicate with a switch using only the read community, you
are assigned the security name ’ReadCommN’. This security name is mapped to
the ’ReadCommG’ group by default. This allows you to view the agent’s MIB tree,
but cannot change any of the values in the MIB tree.
If you communicate with a switch using the write community, you are assigned the
security name ’WriteCommN’. This security name is mapped to the