SNMP Trap Support for the Virtual Switch Interface Master MIB

The VSI master is a software module that resides on a router. The VSI master enables an application to control an ATM switch that is connected to the router. The VSI protocol runs between the VSI master and a VSI slave. The VSI master can communicate with more than one slave across a control interface that connects the router to the switch. Each master/slave connection is called a VSI session. The figure below illustrates VSI sessions between a VSI master and slaves.

Figure 1

VSI Master and VSI Slaves

The VSI Master MIB allows you to monitor the operation of the switch. It also displays the results of the operations. Specifically, the VSI Master MIB allows you to monitor:

• Connections between the router and the controlled switch.
• The status of the interfaces in the switch
• Virtual circuits (VCs) that are maintained across the interfaces.

• MIB Traps
  
• MIB Objects
  

1.    enable

2.    show running-configuration

3.    configure terminal

4.    snmp-server community string RO

5.    exit

6.    write memory

1.    enable

2.    show running-configuration

SNMP notifications can be sent as traps or inform requests. A trap is an unsolicited message sent by an SNMP agent to an SNMP manager, indicating that some event has occurred. You can enable SNMP traps for the VSI Master MIB through the command line interface (CLI) or through an SNMP MIB object. The following sections explain these options.

• Enabling the VSI Master MIB Traps by Using Commands
  
• Enabling the VSI Master MIB Traps by Using SNMP MIB Objects
  

When cross-connects on XtagATM interfaces are created or deleted, a counter keeps a tally of the available logical channel number (LCN) resources. If the LCN resources become too low, the MIB sends messages to alert you of the possibility of resource exhaustion.

You must first set the warning and alarm thresholds for the number of LCNs. To set the warning threshold, use the vsiAvailableChnlWarnThreshold MIB object. To set the alarm threshold, use the vsiAvailableChnlAlarmThreshold MIB object. The following list explains the usage guidelines of these MIB objects:

• The threshold range is 1 to 100.
• The warning threshold value must be greater than or equal to the value of the alarm threshold. Likewise, the alarm threshold value must be less than or equal to the value of the warning threshold.
• If you only set one threshold, the MIB automatically sets the other threshold value to the same value as the threshold value you set.
• By default, the threshold functionality is disabled.

The following list explains the conditions under which warnings, alarms, and other messages are sent. The figure below illustrates the thresholds.

• If the number of LCNs falls below the the warning threshold, a warning is sent. This message indicates that the potential for resource exhaustion is possible.
• If the number of LCNs falls below the alarm threshold, an alarm is generated. This message indicates that the potential for resource exhaustion is imminent. If resource exhaustion occurs, cross-connects cannot be set up.
• If the number of LCNs returns to above the warning threshold, a recovery message is generated. This message means that the potential for resource exhaustion no longer exists.
• If the number of LCNs never crosses any threshold during the polling period, a normal message is generated.

To prevent an overwhelming number of warnings or alarms from being generated during a sampling period, only one warning or alarm is generated when the number of LCNs falls below the threshold. The number of LCNs must return to normal before another warning or alarm is generated.

Figure 2

Warning and Alarm Thresholds

Note

If XtagATM interfaces share resources, the LCN does not represent the actual amount of available resources. For example, the interfaces XtagATM1 and XtagATM2 share resources. If a cross-connect is set up on XtagATM1 but not on XtagATM2, XtagATM1 takes resources away from XtagATM2. When the VSI slave reports the available resources, it only reports on the resources for XtagATM1. The resources for XtagATM2 are not reported. This is because the VSI slave provides updates only when a cross-connect is set up or torn down or when the slave's resources are partitioned. Any interfaces that are not set up or torn down do not send updates. As a result, if XtagATM2 doesn't have enough resources in the resource pool, the problem does not get reported.

In the following example, the SNMP agent is enabled.

snmp-server community

In the following example, SNMPv1 and SNMPv2C are enabled. The configuration permits any SNMP manager to access all objects with read-only permissions using the community string public.

snmp-server community public
 

In the following example, read-only access is granted for all objects to members of access list 4 that specify a community string named comaccess. No other SNMP managers have access to any objects.

snmp-server community comaccess ro 4

In the following example VSI Master MIB traps are sent to the host cisco.com. The community string is restricted. The first line enables the router to send VSI Master MIB traps in addition to any traps previously enabled. The second line specifies the destination of these traps and overwrites any previous snmp-server host commands for the host cisco.com.

snmp-server enable traps vsimaster 
snmp-server host cisco.com restricted vsimaster