Hi,
we get network issues, if one of our employees build a loop on a desktop switch in his/her office.
My test enviroment looks like this.
Switch A is a Cisco 4500 with SUP7 and IOS Version 03.03.00.SG. Switch B is an unconfigured Netgear GS108T Desktop-Switch.
With the factory default configuration of Switch B, Spanning Tree is disabled and BPDUs are not forwarded.
Switch B is connected to gi2/1 of Switch A. This is the current port configuration of gi2/1.
interface GigabitEthernet2/1
switchport access vlan 99
switchport mode access
switchport port-security
switchport port-security violation restrict
spanning-tree portfast
spanning-tree bpduguard enable
ip dhcp snooping limit rate 10
end
If I directly connect two ports of Switch B, Switch B is knocked out. However, my problem is that this loop is not detected by Switch A, which results in 99 % cpu load on Switch A.
I'm pretty certain that a Cisco 3750, IOS Version 15.0(2)SE4 is able to detect these loops and then put the uplink to the desktop switch in err-disable state.
Is there a way to enable this loopback detection feature on my 4500?
Thanks
Timo
