Cisco CNS Network Registrar User's Guide, 5.5
Appendix: SNMP Notification
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SNMP Notification

Table Of Contents

SNMP Notification

How Notification Works

Handling Notification Events

Low Disk Space SNMP Trap

SNMP Troubleshooting

SNMP Notification

The Network Registrar Simple Network Management Protocol (SNMP) notification support allows you to be warned of error conditions and possible problems with the Network Registrar DNS and DHCP servers, and to monitor threshold conditions that may indicate failure or impending failure conditions.

How Notification Works

Network Registrar SNMP notification support allows a standard SNMP management station to receive notification messages from the two servers. These messages contain the details of the event that triggered the SNMP trap.

Network Registrar generates notifications in response to predetermined events that are detected and signaled by the application code. In addition to the knowledge that a particular event occurred, each event can also carry with it a particular set of parameters or current values. For example, the free-address-low-threshold event may occur within the FDDI-Devices scope with a value of 10 percent free. Other scopes and values are also possible for such an event and each type of event may have different parameters associated with it.

Table E-1 describes the events that can generate notifications.

Table E-1 Notification Events 

This event...

Address conflict with another DHCP server detected

Notification when an address conflict with another DHCP server is detected.

Configuration mismatch

Notification when a configuration mismatch between DHCP failover partners occurs.

DNS queue becomes full

Notification when the DHCP server's DNS queue fills and the DHCP server stops processing requests. This is a rare internal condition.

Duplicate IP address detected

Notification whenever a duplicate IP address is detected.

Change in free address count

Free-address-low trap when the number of free IP addresses becomes less than or equal to the low threshold; or a free-address-high trap when the number of free IP addresses exceeds the high threshold.

Other server not responding

Notification when another server (DHCP, DNS, or LDAP) stops responding to the DHCP server.

Other server responding

Notification when another server (DHCP, DNS, or LDAP) responds after having been unresponsive.

Server start

Notification whenever the DHCP or DNS server is started or re-initialized.

Server stop

Notification whenever the DHCP or DNS server is stopped.

Handling Notification Events

When Network Registrar generates a notification, a single copy of the notification is transmitted as an SNMP Trap Protocol Data Unit (PDU) to each recipient. The list of recipients and other notification configuration information are shared by all events (and scopes) and are read when the server is initialized.

Using the CLI

You configure notifications using the trap command. The notification configuration information is persistent and is re-initialized when you run the reload command on the respective server. For more information about configuring notifications, see the trap command section in the Network Registrar CLI Reference Guide.

To use SNMP notifications on your system, you must specify trap recipients. These recipients indicate where Network Registrar notifications are directed. By default, all notifications are enabled, but no trap recipients are defined. Until you define the recipients, no notifications are sent. For details about adding recipients, see the trap addRecipient, listRecipients, and removeRecipient command sections in the Network Registrar CLI Reference Guide.

Network Registrar implements SNMP Trap PDUs according to the SNMP v1 standard. Each trap PDU contains:

Generic-notification code, if enterprise-specific.

Specific-notification field that contains a code indicating the event or threshold crossing that has occurred.

Variable-bindings field that contains additional information about certain events.

Refer to the Management Information Base (MIB) for the details. You can find the MIB in the locations based on the operating system in the following subsections. The MIB requires the following MIB files to compile:

These individual Management Information Bases (MIBs) are available at the following public website:

MIB Location on UNIX


MIB Location on Windows

\ProgramFiles\Network Registrar\Misc\ 

Low Disk Space SNMP Trap

The Network Registrar mcdshadow utility generates a new SNMP trap if the utility cannot create a shadow backup of the data due to inadequate disk space. See the "Checking MCD Database Integrity" section.

SNMP Troubleshooting

To diagnose Network Registrar conditions, set the following SNMP traps using the CLI. These traps ensure that a central monitor is informed when unexpected events occur, so that you can respond more quickly before things become critical.

nrcmd> trap show 
nrcmd> trap enable address-conflict 
nrcmd> trap enable dhcp-failover-config-mismatch 
nrcmd> trap enable other-server-not-responding 
nrcmd> trap enable free-address-low 
nrcmd> trap set free-address-low-treshold=15% 
nrcmd> trap set free-address-high-treshold=30% 

You can also set the following traps:

nrcmd> trap enable server-start 
nrcmd> trap enable server-stop 
nrcmd> trap enable free-address-high 
nrcmd> trap enable dns-queue-too-big 
nrcmd> trap enable other-server-responding 
nrcmd> trap enable duplicate-address 

nrcmd> trap set free-address-low-treshold=15% 
nrcmd> trap set free-address-high-treshold=30%