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Real life: Dealing with a rogue ISP

20.10.2006
The IEEE 802.3 standards exist to ensure interoperability between Ethernet devices. But what happens when different interpretations of the standards leads to interoperability issues between networks that use standards-compliant equipment? Usually a lot of finger-pointing, and unless the different network administrators work together to find an acceptable solution, connectivity will not happen.

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.