Loop Protection
The ProCurve switches have a feature which gets around one of the limitations of spanning tree. If a loop is created on a dumb switch downstream of the ProCurve, Spanning Tree may not detect the loop.
Enter the ‘loop-protect’ feature. Similar to spanning tree, it sends a broadcast probe out every five seconds and if it gets it back, it decides there is a loop and downs the port.
To enable:
# conf t
# loop-protect (ports)
# exit
The word ‘all’ can be used instead of a list of ports.
To see what is going on during network problems: connect to the console or telnet, and issue the command:
# show loop-protect all Transmit Interval (sec) : 5
Port Disable Timer (sec) : Disabled
Loop Detected Trap : Disabled
Loop Loop Loop Time Rx Port
Port Protection Detected Count Since Last Loop Action Status
---- ----------- --------- ---------- ---------------- ------------ --------
A1 No No 0 send-disable Up
A2 Yes No 0 send-disable Up
A3 Yes No 0 send-disable Up
A4 Yes No 0 send-disable Up
A5 Yes No 0 send-disable Up
A6 Yes No 0 send-disable Down
A7 Yes No 0 send-disable Down
A8 Yes No 0 send-disable Down
A9 Yes No 0 send-disable Down
A10 Yes No 0 send-disable Down
A11 Yes No 0 send-disable Down
A12 Yes No 0 send-disable Down
A13 Yes No 0 send-disable Down
A14 Yes No 0 send-disable Down
[…]
Obviously the port which has “yes” for “Loop Detected” is the one with the loop. Resolution of the looping issue is left as an exercise for the reader.