Mechanism to maintain current state of network elements

Overview

NFM-P uses several mechanisms to maintain and display the current state of the network elements it manages. These mechanisms can include:

These mechanisms are built into the Nokia 7950 XRS, 7750 SR, 7450 ESS, 7450 SR, 7210 SAS, and 7705 SAR network elements and the NFM-P network element interaction layers.

IP connectivity (ping) verification

NFM-P can be configured to ping all network elements at a configurable interval to monitor IP connectivity. If the network element is unreachable, an alarm will be raised against the network element. Details of the alarm are the following:

Ping verification is disabled by default. IP connectivity checks using ping must be scheduled through the default policy.

SNMP connectivity verification

NFM-P performs an SNMP communication check every 4 minutes. If NFM-P can not communicate via SNMP with a network element, it will raise a communications alarm against that network element. NFM-P will also color the network element red on the map to indicate the communication problem. NFM-P will clear the alarm and color the network element as green once NFM-P detects SNMP connectivity to the network is re-established. Details of the alarm are the following:

This behavior occurs by default and is not configurable.

SNMP traps

NFM-P listens to SNMP traps to receive changes from the network elements. NFM-P configures the trap log ID on each network element when it is first discovered. The network element then uses that trap log ID to send all configuration changes and updates to NFM-P. The NFM-P will react to the traps it receives and make appropriate changes to the database, alarms and related object as required.

SNMP trap sequence verification

NFM-P retrieves the last trap sequence number sent from all network elements at a configurable interval. This interval is configurable on a per resource group basis. Resource groups allow the user to configure the communications behavior of a group of network elements. By default, the core resource group includes all network elements, and verifies the trap sequence number every 4 minutes. NFM-P compares that sequence number with the sequence number of the last trap it received from that network element. If they do not match, NFM-P will request only the missing traps from the network element. If at any point NFM-P realizes that it is missing more than 200 traps from a network element, or if the network element no longer has the missed trap, NFM-P will request a full resynchronization on that network element rather than just request the missing traps.

This behavior occurs by default and is not configurable.

Scheduled SNMP MIB polling

NFM-P can poll all data SNMP MIBs from the network elements at a configurable interval. The Polling Policy is disabled by default. This behavior is configurable via the Polling tab of the network elements properties form.

Network outages and recovery

When a Nokia 7x50 based network element loses visibility of the NFM-P, it is unable to send traps to the network manager, and the traps are queued on the network element. SNMP trap sequence verification describes NFM-P behavior with regards to trap handling. When a network outage occurs, the network element configuration in NFM-P will be made consistent with the network element, but any event notifications, such as SNMP traps, that occurred during the network outage will not have been processed. This will cause intermediate state change alarms to not be reflected in NFM-P during the network outage.