Showing results for 
Search instead for 
Did you mean: 

Unmanaged switch loop prevention connected to 460-G2

Unmanaged switch loop prevention connected to 460-G2

New Contributor III
So we have a bunch of 460-G2's we will be replacing some enterasys C2's. Currently SpanGuard on the C2's was not enabled hence when people with an unmanaged desk switch looped 2 of the ports all hell breaks loose with Spantree.

The 460-G2's have STP enabled with BPDU-restrict and also edge-safeguard, but this does not prevent unmanaged switch loops.

How can we prevent the STP from people looping an unmanage switch connected to only 1 edge port and trashing the network?

New Contributor II
With Spanning tree the port will block, obviously the unmanaged switch will be down until the loop stops. ELRP does work well but in my experience customers forget where its configured or configure it on uplinks by mistake, resulting in the " every now and then one of my sites is down, we reboot and it comes back " issues.

New Contributor III
figured the issue.

the Unmanaged switch already has a broadcast storm happening on it and when the BPDU's get sent from the 460-G2 it takes X amount of time for that to get inserted into the processor of the unmanaged switch.

If loop the unmanaged switch and straight away connect to the 460-G2 it disables the port. 

If the ELRP VLAN is on both ports it should catch the loop. Does the log show the loop?

how can i check for that?
By default we are going to disable the port.

This works with 2 seperate ports on same vlan are loop with 2 different ports on switch.
This works for connecting unmanage switch and then loop the unmanaged switch on itself.
This work if i connect unmanage switch, then connect it to another port on same VLAN

I tested again and first time i connected an already looped on itself unmanaged switch it turned the port off. i left the switch for a minute then connected to another ports and then its xmas time with the lights.

if i check ELRP disabled ports the ports appear on the list, except the issue i am having.