BGP4-MIB::bgpBackwardTransition #

The BGPBackwardTransition Event is generated when the BGP FSM moves from a higher numbered state to a lower numbered state.

Variables #

• bgpPeerLastError
• bgpPeerState

Definitions #

bgpPeerLastError

The last error code and subcode seen by this peer on this connection. If no error has occurred, this field is zero. Otherwise, the first byte of this two byte OCTET STRING contains the error code, and the second byte contains the subcode.

bgpPeerState

The BGP peer connection state.

Runbook for BGP4-MIB::bgpBackwardTransition SNMP Trap #

Meaning #

The BGPBackwardTransition Event is generated when the BGP Finite State Machine (FSM) moves from a higher numbered state to a lower numbered state. This trap indicates that the BGP connection has regressed to a previous state, which can impact network convergence and stability.

Impact #

• Potential loss of network connectivity or intermittent connectivity issues
• Increased latency and packet loss due to BGP reconvergence
• Possible routing table instability affecting network services and applications
• Increased network operations workload due to troubleshooting and recovery efforts

Diagnosis #

To diagnose the root cause of this issue:

1. Verify the BGP peer connection state using the bgpPeerState variable.
2. Check the last error code and subcode seen by the peer using the bgpPeerLastError variable.
3. Analyze BGP log files and debug messages to identify the specific error or event that triggered the backward transition.
4. Review network topology and configuration changes that may have contributed to the issue.
5. Perform a thorough analysis of BGP neighbor relationships and peer connections.

Mitigation #

To mitigate the impact of this issue:

1. Immediately investigate and address any underlying errors or issues identified in the diagnosis process.
2. Verify BGP peer connectivity and re-establish connections as necessary.
3. Perform a soft reset of the BGP process to reload the configuration and re-establish peer relationships.
4. Consider adjusting BGP timers and damping parameters to improve network convergence and stability.
5. Implement additional monitoring and logging to detect and respond to future BGP backward transition events.
6. Consider performing a network-wide BGP audit to identify and address any underlying configuration or design issues.