isisAttemptToExceedMaxSequence

ISIS-MIB::isisAttemptToExceedMaxSequence #

When the sequence number on an LSP we generate wraps the 32-bit sequence counter, we purge and wait to re-announce this information. This notification describes that event. Since these should not be generated rapidly, we generate an event each time this happens. While the first 6 bytes of the LSPID are ours, the other two contain useful information.

Variables #

  • isisNotificationSysLevelIndex
  • isisPduLspId

Definitions #

isisNotificationSysLevelIndex
The system level for this notification.
isisPduLspId
An Octet String that uniquely identifies a Link State PDU.

Here is a runbook for the SNMP trap ISIS-MIB::isisAttemptToExceedMaxSequence:

Meaning #

The ISIS-MIB::isisAttemptToExceedMaxSequence trap indicates that the sequence number on a Link State PDU (LSP) generated by the device has wrapped the 32-bit sequence counter. This causes the device to purge and wait to re-announce the information. This trap is generated each time this event occurs.

Impact #

The impact of this trap is that the device will temporarily stop announcing the affected LSP, which may lead to temporary inconsistencies in the network topology. This can cause routing issues and affect network availability.

Diagnosis #

To diagnose the cause of this trap, follow these steps:

  1. Check the isisNotificationSysLevelIndex variable to determine the system level at which the notification was generated.
  2. Examine the isisPduLspId variable to identify the specific LSP that triggered the trap.
  3. Verify that the LSP is correctly configured and that there are no issues with the underlying network infrastructure.
  4. Check the device’s logs for any other related errors or issues that may be contributing to the sequence number wrap.

Mitigation #

To mitigate the effects of this trap, follow these steps:

  1. Ensure that the device has sufficient resources and is not experiencing high CPU or memory utilization.
  2. Verify that the LSP is correctly configured and that there are no issues with the underlying network infrastructure.
  3. Consider increasing the sequence number space or adjusting the LSP announcement timers to reduce the likelihood of sequence number wrap.
  4. Implement a monitoring system to detect and alert on this trap, allowing for prompt investigation and resolution.
  5. If the issue persists, consult the device vendor’s documentation or contact their support team for further assistance.
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