Recently, I encountered such a situation when trying to connect a large LAN to a new Internet link. However, by employing patience with solid troubleshooting and carefully researching the pertinent standards, I was able to turn a classic finger-pointing situation into a functional network connection.
The task
On the surface, the task seemed to be quite basic. I was upgrading a customer's LAN Internet connection to a 1Gbit/sec. Metro Ethernet link. Now, having an Ethernet feed presented the opportunity of placing an intrusion-detection system (IDS) sensor prior to the border router by connecting the Metro Ethernet to a switch placed between the LAN border router and the Metro Ethernet drop, as shown in Figure 1.
The problem
When I connected the switch to the ISP's equipment via a multimode fiber patch cord, the ISP equipment had a link light but the LAN equipment did not. I tested the connection to verify that it was in fact inoperable.