I have a small and inexpensive ethernet switch which is giving me some headache. For some reason some devices only work when I plug them into specific ports. The ports are not broken, as other devices work on the same ports. Also, if I just take the cable from one of the ports that doesn't work and plug it into another port, it works fine.
When I say the devices don't work, they actually show activity on the LEDs such as LINK and ACT, but I can't ping them, but I have no explanation. I also tried to restart the switch, computer, flush ARP cache etc.
I read that some switches have automatic MAC address aging and learning. Could that be related?
They reason why I am asking is because soon I will undergo a massive operation where we have to connect hundreds of these devices to the network, and we plan to buy 48 port switches for this purpose. If they start playing strange games like this, I am absolutely unsure what is going on.
Could this be a problem with the switch, is this expected, or do you believe it is rather a computer problem or router problem (the switch is connected to a router), but I am not using a gateway on these devices or the computer (and as said, as soon as I plugin the devices on a different port, they start working).
Best Answer
Just because some devices will link doesn't mean the switch isn't still bad. Some NICs will be more tolerant of marginal signaling and/or timing.
Personal example... I have a Nortel ERS with a damaged clock circuit (power outage killed it.) I've verified with a scope that the clock for the second half of the switch is noisy and marginally out of spec. As a result, some network cards will link, and actually function. However, most, including the other half of the switch and every other switch I have, won't. 10M works fine, because the PHYs generate their own clock. 100M only works with "loose" NICs. 1000M won't even link with itself -- that signal is pure noise.
Cheap switches are cheap for a reason. I'm not going to say how many sub-50$ "hubs" I've thrown away.