Today I investigated a networking issue. An entire lab of computers lost all network connectivity; they had link lights, but couldn't get DHCP or reach anywhere. I decided to do some cable tracing, since link lights appear even when there's a connection to a switch that doesn't go anywhere. I found several problems: first, two switches seemed to be connected cyclically. Unplugging one cable restored connectivity for some computers. Then, I found another switch looped back into itself. Fixing that and reconnecting the cable to the right switch did the trick for the rest of the machines.
When working with simple (i.e. cheap, non-fancy) switches, loops can cause everything to grind to a halt. Broadcasts just keep flying around and clogging up the cables, thereby blocking more interesting communication.
No comments:
Post a Comment