Router Rejecting Network Messages

Overview:

The "Router Rejecting Network Messages" diagnostic fails when a BACnet router in an Operational Technology network refuses to forward or pass on certain network messages, data packets, or communication requests. This rejection can occur for various reasons and can impact the flow of information and communication within the network.

Causes:

• (Mis)configured Access Control Policies: BACnet routers are often configured with access control policies that determine which types of messages or packets are allowed to pass through. If a router's access control rules are set to reject specific messages, those messages will be blocked.
  
• Security Measures: Routers may reject network messages that are flagged as potential security threats, such as malicious traffic or unauthorized access attempts.
  
• Resource Overload: If a router is handling a high volume of traffic or experiencing resource constraints, it may reject certain messages to manage its workload.
  
• Network Configuration Errors: Misconfigured routers might inadvertently block legitimate network messages due to incorrect settings.
  
• Software or Firmware Bugs: Software bugs or firmware issues within the router's operating system can lead to incorrect message rejection.

Implications:

• Communication Breakdown: When a router rejects network messages, it disrupts the communication flow between devices and segments of the network.
  
• Data Loss: Rejected messages may contain critical data, and their rejection can lead to data loss or incomplete communication.
  
• Delays: Routers rejecting messages may lead to increased delays in data transmission and response times.
  
• Operational Issues: Rejected messages can affect the functionality of applications, services, and devices that rely on timely and accurate communication.
  
• Network Inefficiency: Rejected messages can cause retransmissions and extra overhead, reducing network efficiency.
  
  

How to fix it:

• Configuration Review: Verify the router's access control policies and configuration settings to ensure they align with the network's requirements.
  
• Security Measures: Assess security settings to ensure they are appropriately configured to prevent false positives while still blocking potential threats.
  
• Resource Monitoring: Monitor router performance and resource usage to identify and address resource-related issues.
  
• Testing: Conduct testing and simulations to reproduce rejected messages and identify the underlying causes.
  
• Software/Firmware Updates: Keep router software and firmware up to date to address known bugs or issues that could lead to message rejection.