As an IT professional dealing with enterprise networking, you may encounter situations where the number of BGP (Border Gateway Protocol) neighbor routing entries exceeds the limit set by your service provider. This issue can arise unexpectedly and cause disruptions in your network connectivity, particularly when relying on MPLS (Multiprotocol Label Switching) lines from telecommunications companies. In this article, we'll explore a real-world scenario where a company faced a problem with their BGP neighbor routing entries exceeding the limit, and how they approached the resolution. The Scenario: The company had two lines, one of which was a telecom MPLS line. They needed to pass the route to the telecom's BGP route, allowing the telecom's BGP routing protocol to be transmitted to the corresponding routing table at the company's headquarters. The Problem: Suddenly, the telecom MPLS line experienced a failure, prompting an alert from the network monitoring system (NETCARE). Initially, it was suspected that the fiber optic cable was broken, and the network team arranged for troubleshooting. However, the issue turned out to be related to the number of routing entries published, which exceeded the limit of 20 set by the telecom provider. Troubleshooting Steps: 1. The network team connected to the company's core switch to check the routing releases using the "show ip route eigrp 1" command, but no abnormalities were detected. 2. They then examined the establishment of the EIGRP1 neighbor directly connected to the telecom using the "show ip eigrp nei" command, which revealed that the neighbor was down due to a holding time expiration. 3. Attempting to re-establish the neighbor using the "clear ip eigrp nei" command did not resolve the issue. 4. Further investigation revealed that the port connecting the telecom's device and the company's core device had become half-duplex, causing the line to break intermittently. The Solution: The telecom provider's team logged into their equipment and found that the port configuration had changed to half-duplex mode. By reconfiguring the interface speed and duplex settings using the "interface speed 100 duplex full" command, they were able to resolve the issue. Lessons Learned: This incident highlighted the importance of effective communication and coordination between service providers and customers. In this case, the telecom provider made changes to their configuration without notifying the customer, leading to unexpected behavior and network disruptions. To prevent similar issues in the future, it is crucial to establish clear communication channels and change management processes with service providers. Regular monitoring and proactive troubleshooting can also help identify potential problems before they escalate. By understanding the root cause and implementing the necessary configuration changes, the company was able to resolve the issue of BGP neighbor routing entries exceeding the limit and restore their network connectivity.