Narrow down problematical network device in
Situations: The client has over 20 Cisco switches connecting to 3
buildings in the campus.
1. All Canon printers restart automatically and continually. Can't ping the
Canon printers' IP addresses and the printers can't communicate with printer
2. Laptops keep losing the connection and can't ping the wireless AP IP
3. The wireless AP keeps disappearing from the monitor and keeps change the
4. When ping the Dell iDRAC, it gets a lot time out.
Troubleshooting: 1. After shutting down a switch which is located in the
center building, every thing works fine.
2. After turning the switch on and disabling the port connecting to next
switch, every thing works fine. So, we know the problem is the next switch
or a device behind this switch. Note: don't disable the port on the remote
switch. Otherwise, you must turn on it back by using console connection.
3. Continue to test until finding out the problematical switch. Then disable
individual port until find the problematical device.
In our case, it is 3COM router. After unplug the 3COM router, every thing