A tricky question - please help me out providing your views/ans..
How would you identify a L2 switch loop in a big network? Imagine there are many L2 switches in a big organization each connected at different floors. By mistake an user connected an ethernet cable over the switch ports back to back creating a loop. This would eventually make the entire network stormed with broadcasts bringing it down.
The scenario has no STP running on the nework. How can we identify immediately where the loop is instead of searching for the port physically on each floor which is time consuming. let me know if you any commands or troubleshooting technique that we can easily simplify and find out the problem.
I haven't done this so far but i got some solution regarding this in the following link
When a bridging loop occurs you will usually see multiple interfaces with a high output rate and low input rate and a single interface with a high input rate and low output rate.
- Trace the port with the high input rate down until you come to an access port and shut it down
- If the port with the high input rate leads you into a loop you will want to check spanning tree states until you either find a switch that has a port in an incorrect forwarding state or some other reason that is causing us to loop packets.
I assume your using vlans or mpls? Or what protocol are u using for your l2 network? It doesn't make too much sense to be without a loop prevention mechanism when u have a variety of protocols at your disposal. Eg, rapid pvst, portfast, bdpu guard etc. Usually when loops occur you see increased CPU utilization, you can check #sh processes CPU. What your asking is something that can be very quickly avoided by using spanning tree and enabling portfast on all access ports. It can be very difficult to identify exactly the cause of the problem otherwise