Administrator Guide

1. Enter Configuration mode.
CONFIGURATION mode
Dell(conf)# mac-address-table station-move threshold number interval seconds
• number is the threshold value. The range is from 5 to 50.
After you enter a threshold value, you can specify a time interval in seconds. The range is from 1 to 60 seconds.
Dell(conf)# mac-address-table station-move threshold 5 interval 30
NOTE: Dell Networking OS recommends that you use the command because xSTP protocols are not supported on
PEs.
2. If a station move for a MAC address is detected above the configured threshold and within the specified time, a syslog message is
triggered with the port information. All ports on which the station move was detected are shut down, except the old interface. For
example:
Jun 18 09:55:35: %RPM0-P:RP %MACMGR-1-PE LOOP DETECTION: Loop occurred on PE
interfaces:oldInterface: peGigE 0/2/47, newInterface: peGigE 0/1/20,vlanId: 3902, macAddr:
00:aa:00:00:00:
3. When a PE interface is shut down due to a PE loop detection, you must manually reset it. To reset the interface, shut it down by
entering the shutdown command and then re-enable it by entering the no shutdown command.
4. To display the PE ports that are shut down due to loop detection, enter the show mac learning-limit violate-action
command.
Dell# show mac learning-limit violate-action
Interface Violation-Type Violate-Action Status
PeGi 0/2/47 Pe-Loop Shutdown PEloop-disable
PeGi 100/0/20 Pe-Loop Shutdown PEloop-disable
PeGi 255/0/47 Pe-Loop Shutdown PEloop-disable
Po 1 Pe-Loop Shutdown PEloop-disable
Po 100 Pe-Loop Shutdown PEloop-disable
5. To display the reason why the line protocol is down on a PE port or port channel, enter the show interface command.
EXEC mode
Dell(conf-if-po-1)#do show interface port-channel 1
Port-channel 1 is up, line protocol is down(Pe Loop Detection)
This section covers the enhancements to this feature based on scenarios in Dell Networking OS 9.11.2.0:
Loop caused due to mis-cabling across PEs or within a PE
• Two PE interfaces PEX1 and PEX2 are looped back wrongly due to mis-cabling.
• Both the interfaces are assigned to a VLAN which is assigned an IP address.
A simple ping for an IP address in the subnet will result in a continuous loop without being detected. The reason being we don’t learn our
own MAC address and hence, the MAC station move is never detected. Without station moves, the existing PE Loop Detection Feature
would not kick-in. If there is no data traffic on the LAN to detect the loop, the control PDUs like LACP, LLDP, ARP, DHCP etc., will be
used to detect loops at PE.
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Port Extenders (PEs)