Several Linux machines/servers need access to the internet in my workplace. Due to the lack of lan ports in my work area, I use a gigabit switch (DLink 1224T) to "split" the internet so that all these machines can get online.
However the incoming link from the lan port always goes down after a period of time. After some testing, I found that :
1) The incoming link drops when more than 2 machines are connected to the switch. When I connect a 3rd machine, the incoming link will go down, causing all 3 machines to be offline. Prior to that, the first 2 machines have no issues at all.
2) It doesn't matter which lan port I use for the incoming link, the issue remains
3) The link comes up again after about 5 minutes, only to go down again after a short period if more than X machines are connected.
I'm wondering if this is some switch configuration issue on my side or the IT side, or some weird Linux networking issue.
what device is the gigabit Dlink switch plugged into. Sounds like a port security configuration on a cisco switch which causes the port to go into the err-disabled state when it sees more than 2 mac addresses on the port. This can be set to bring the port back up after a certain period of time.
Start your troubleshooting with the network device that the single ethernet connection comes from. Its probably a configuration issue on that device.