This is the second article in our "Troubleshooting War Stories" series, and this one will be shorter and dive into an incident with the corporate core switch. I recently received a call from a network administrator at a major government corporation. He told me their core . Are you a member of CheckMates? Sign in with your Check Point UserCenter/PartnerMap account to access more great content and get a chance to win some Apple AirPods! If you don't have an account, create one now for free! 2019-10-01 06:05 AM Hey There So we are runing a Old Cisco Nexus 5000K Switch. We have a pair of Dell N3224P-ON switches and today's morning my colleague gave me a task and instructions to remove some unused VLANs. I'm sure I removed the correct VLANs. When I saved the configuration, everything stopped working and now we don't know what to do. We already rebooted both. The problem of switch failure generally includes physical layer failure, port negotiation and self-loop issues, Vlan issues, device compatibility issues, and other problems. Its primary function is to rapidly forward data packets between different aggregation switches and, ultimately, to the internet.