Setup Guide
• If there is a match, the kernel noties L2Mgr about the loop detection and L2Mgr would in turn, bring down the appropriate PE
interface and show an appropriate syslog to the user to correct the loop.
Loop caused due to mis-cabling in an un-managed L2 switch
• An un-managed layer 2 switch is connected to a PE.
• There is some mis-cabling in the L2 switch.
This can result in loops. The current PE loop detection mechanism with data
trac MAC station move, can possibly bring down the other
PE interface which is not connected to the L2 switch, thereby keeping the loop active.
The rst recommendation is to enable xSTP on the un-managed switch. The uplink port connected to the PE must be made as an edge
port in the L2 switch. This would ensure the local loop in the L2 switch is cut by itself without having to bring down any of the PE
interfaces. Bringing down the PE interface would still keep the loop active in the switch which aects all the hosts connected to the L2
switch.
In the event of the L2 switch not supporting xSTP (hub etc), the control PDUs will be used to detect loops at PE to mitigate the eect of
the loop in other parts of the network.
Loop between a LM interface and PE interface
• A LM (Line Module) interface P1 is connected to a L2 switch.
• A PE interface, PEX1 is connected to the same un-managed L2 switch.
Port Extenders (PEs)
765