In reading last week’s 12 things to know when troubleshooting your network post, a particular chord was struck with me in the physical layer verification section of the document. That chord is the ongoing battle with unmanaged switches in an enterprise network. The practice of users putting up unmanaged switches and hubs is a pet peeve of many network administrators, as well as generally forbidden by policy though not always enforced by the managed switches.

Knowledgeable workers are generally smart enough to obtain a network switch and uplink it to the company network, and the onus is on the network administrator to correct any subsequent issues that arise. While this is usually harmless, it can sometimes go awry. Here are some situations that I’ve seen in my time:

  • Using the built-in switch of a router as a switch. This is the good old rogue DHCP server battle with a new twist. The user was using a DSL router that was used in the branch office as a switch on their desk. Here is the crazy part, the user had uplinked and simply “got used” to getting the correct DHCP address or the closed branch office’s network — that went to nowhere. The DSL router even had a label of the city that the branch office was located on the top — and that was a thousand miles away.
  • Uplink loop. Having a switch uplinked twice to the network or to another switch two times makes for a pretty graph of network utilization, yet it becomes incredibly inefficient at moving packets.
  • Broadband router and switch. One user had been using a wireless broadband router with the Internet connection of the data card because the Internet content filtering was annoying.

These accounts come from remote sites that don’t have an IT staff footprint locally, and in many accounts the users truly think that they are on their own. The stories are out there, and surely you have had some sort of run-in with a remote switch that has stirred you up. Please share your stories below.