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Loop Protection

Created by dave. Last edited by dave, 15 years and 122 days ago. Viewed 27,342 times. #1
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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.

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