I thought it would be a good idea to start a series using the NetworkDataPedia’s theme of ‘knowing your network.
Let’s start at layer 1 or the hardware layer.
Unfortunately, there is so much that can go wrong at this layer that I cant possibly cover it in one article. I see a lot "you have a network connection and life will seem fine" attitude. This is unfortunate because if the problems would cause an complete outage, you would be forced to address it instead of ignoring it.
I find that many physical level issues are grouped into a few categories:
Installation and Support
I have seen many issues caused by improper installation, and support shortcuts. For example, I’ve seen CAT5 unshielded cable wrapped around a welder, cat3 RJ45 couplers to combine 2 cat 5 cables, unsupported bundle of cables pulling the RJ45 connectors out from the switch, overheating modem in a plastic bag hanging in a cabinet, dirty fibre optic cables and equipment ports.
And that’s just what I can remember at the moment. I’m sure you have a bunch yourselves.
Inheritance
Many times analysts build on to an existing system not knowing or understanding the whole picture. A great example is where I saw half the cable run using shielded twisted pair cabling and the new run was unshielded. When I asked why they wouldn’t continue the shielded cabling, the contractor said, ”no one uses that stuff anymore”. Unfortunately I checked the entire run of shielded cables and in my opinion shielded cabling was required since it was running through a factory and outside. The client brushed it off and I later found out they had to replace the cabling due to ‘excessive errors on the new cable runs’. Oops...
When possible, the best way to start at the physical layer is to ‘go for a walk’. Either follow a connection from a host to the network, or verify the installation documentation. In this day of video conferencing and smartphones, you can even do this remotely by having someone walk around with their phone while using facetime or zoom.
I have learned a lot working on network cleanup/network migration projects and everyday installations since there is always a surprise to overcome.
