Watermarks

Watermarks can be configured to monitor the actual usage of sessions, ports, and port blocks.

For each watermark, a high and a low value must be set. When the high threshold value is crossed in the upward direction, an event is generated (SNMP trap), notifying the operator that a NAT resource may be approaching exhaustion. When the low threshold value is crossed in the downward direction, a similar event is generated (clearing the first event, notifying the operator that the resource utilization has dropped below the low threshold value.

Watermarks can be defined on the NAT group, pool, and policy level.

• NAT group

  Watermarks can be placed to monitor the total number of sessions on an MDA.

• NAT pool on each NAT group member

  Watermarks can be placed to monitor the port block occupancy in a pool within each NAT group member.

• policy

  In the policy the operator can define watermarks on session and port usage. In both cases, it is the usage per subscriber (for L2-Aware NAT) or per host (for large-scale NAT) that are monitored.